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TUCoPS :: Password Security :: 1537.txt

Better Password Practices




The Simplest Security: A Guide To Better Password Practices
by Sarah Granger
last updated January 17, 2002
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Refresher – Password Usage

Let’s be honest, passwords are annoying. These days, we need a
password or PIN everywhere. We have so many that we can’t keep
track of them all. We forget to update them; and when we do, it’s
difficult to come up with effective ones that we can still
remember, so we procrastinate changing them for months, even
years. We all know this is bad, but the alternative – the painful,
irritating password creation and memorization process – is
sometimes more than we can tolerate. There is hope! Passwords
don’t have to be complex cryptograms. A few simple methods can
help make living with passwords a little easier.

While we may find them annoying, and even take them for granted,
it is important to remember why passwords are important: passwords
are often the first (and possibly only) defense against intrusion
(MacGregor). They protect personal information – information we
don’t want anyone and everyone to know. In our personal lives,
this means financial information, health data, and private
documents. In a professional context, this may encompass anything
considered crucial to the success of the organization: trade
secrets, financial data, intellectual property, customer lists,
etc.

Passwords are simpler and cheaper than other, more secure forms of
authentication like special key cards, fingerprint ID machines,
and retinal scanners. They provide a simple, direct means of
protecting a system or account. For the sake of this article,
we’ll define a ‘password’ as a word, a phrase, or combination of
miscellaneous characters that authenticates the identity of the
user. Passwords are generally used in combination with some form
of identification, such as a username, account number, or e-mail
address. While a username establishes the identity of the user for
the computer or system, the password, which is known only to the
authorized user, authenticates that the user is who he or she
claims to be. This means that their function is to “prove to the
system that you are who you say you are” (Russell).

Password Cracking

While passwords are a vital component of system security, they can
be cracked or broken relatively easily. Password cracking is the
process of figuring out or breaking passwords in order to gain
unauthorized entrance to a system or account. It is much easier
than most users would think. (The difference between cracking and
hacking is that codes are cracked, machines are hacked.) Passwords
can be cracked in a variety of different ways. The most simple is
the use of a word list or dictionary program to break the password
by brute force. These programs compare lists of words or character
combination against password until they find a match. If cracking
codes seems like science fiction, search “password cracker” on
Packetstorm or Passwordportal.net. There are also numerous
password cracking tools available that any average person can use.
(For more information on password cracking tools, please see the
SecurityFocus article Password Crackers - Ensuring the Security of
Your Password.)

Another easy way for potential intruders to nab passwords is
through social engineering: physically nabbing the password off a
Post-It from under someone’s keyboard or through imitating an IT
engineer and asking over the phone. Many users create passwords
that can be guessed by learning a minimal amount of information
about the person whose password is being sought. (For more
information on social engineering please see the SecurityFocus
series Social Engineering Fundamentals) A more technical way of
learning passwords is through sniffers, which look at the raw data
transmitted across the net and decipher its contents. “A sniffer
can read every keystroke sent out from your machine, including
passwords” (University of Michigan). It’s possible that someone
out there has at least one of your passwords right now.

How To Choose Good Passwords

Now that we have established the importance of passwords and some
of the ways in which they may be vulnerable to cracking, we can
discuss ways of creating good, strong passwords. In creating
strong, effective passwords it is often helpful to keep in mind
some of the methods by which they may be cracked, so let’s begin
with what NOT to do when choosing passwords.

No Dictionary Words, Proper Nouns, or Foreign Words

As has already been mentioned, password cracking tools are very
effective at processing large quantities of letter and number
combinations until a match for the password is found, as such
users should avoid using conventional words as passwords. By the
same token, they should also avoid regular words with numbers
tacked onto the end and conventional words that are simply written
backwards, such as ‘nimda’. While these may prove to be difficult
for people to figure out, they are no match for the brute force
attacks of password cracking tools.

No Personal Information

One of the frustrating things about passwords is that they need to
be easy for users to remember. Naturally, this leads many users to
incorporate personal information into their passwords. However, as
is discussed in the Social Engineering Fundamentals, it is
alarmingly easy for hackers to obtain personal information about
prospective targets. As such, it is strongly recommended that
users not include such information in their passwords. This means
that the password should not include anything remotely related to
the user’s name, nickname, or the name of a family member or pet.
Also, the password should not contain any easily recognizable
numbers like phone numbers or addresses or other information that
someone could guess by picking up your mail.

Length, Width and Depth

A strong, effective password requires a necessary degree of
complexity. Three factors can help users to develop this
complexity: length, width & depth. Length means that the longer a
password, the more difficult it is to crack. Simply put, longer is
better. Probability dictates that the longer a password the more
difficult it will be to crack. It is generally recommended that
passwords be between six and nine characters. Greater length is
acceptable, as long as the operating system allows for it and the
user can remember the password. However, shorter passwords should
be avoided.

Width is a way of describing the different types of characters
that are used. Don’t just consider the alphabet. There are also
numbers and special characters like ‘%’, and in most operating
systems, upper and lower case letters are also known as different
characters. Windows, for example, is not always case sensitive.
(This means it doesn’t know the difference between ‘A’ and ‘a’.)
Some operating systems allow control characters, alt characters,
and spaces to be used in passwords. As a general rule the
following character sets should all be included in every password:

   * uppercase letters such as A, B, C;
   * lowercase letters such as a, b,c;
   * numerals such as 1, 2, 3;
   * special characters such as $, ?, &; and
   * alt characters such as µ, £, Æ. (Cliff)

Depth refers to choosing a password with a challenging meaning –
something not easily guessable. Stop thinking in terms of
passwords and start thinking in terms of phrases. “A good password
is easy to remember, but hard to guess.” (Armstrong) The purpose
of a mnemonic phrase is to allow the creation of a complex
password that will not need to be written down. Examples of a
mnemonic phrase may include a phrase spelled phonetically, such as
‘ImuKat!’ (instead of ‘I’m a cat!’) or the first letters of a
memorable phrase such as ‘qbfjold*’ = “quick brown fox jumped over
lazy dog.”

What may be most effective is for users to choose a phrase that is
has personal meaning (for easy recollection), to take the initials
of each of the words in that phrase, and to convert some of those
letters into other characters (substituting the number ‘3’ for the
letter ‘e’ is a common example). For more examples, see the
University of Michigan’s Password Security Guide.                                               [Image]

Extra Protection

All of the good password cracking programs include foreign words,
backwards words, etc. And the easiest way to steal a password is
by asking for it, so it’s simpler to never give it away.

In some cases, a good password is enough protection to keep out
intruders. In others, it’s just a start. Encryption and one-time
passwords add extra protection to systems. Encryption means
garbling the password to protect from sniffers or other onlookers,
through a particular scheme that can be deciphered from the other
end of the connection. One-time passwords (S/key is the most
commonly used) are just that. They can be used only once. This
requires carrying a list of passwords or having a special password
calculator or SecureCard, but can be a very reliable method of
password security.

There are also certain behaviors that users should practice in
order to maximize the effectiveness of their passwords. Users
should avoid using the same password on multiple accounts. Doing
this creates a single point of failure, which means that if an
intruder gains access to one account, he or she will have access
to all of the user’s accounts. Users should never disclose their
passwords to anybody unless they know them to be authorized (i.e.,
systems administrators). Even then, passwords should only be
disclosed in person (not over the phone or by e-mail) to a known,
trusted source.

Users should exercise extreme caution when writing down or storing
passwords. Stories of hackers obtaining passwords through
shoulder-surfing and dumpster diving are not urban myths, they are
real. Users should resist the temptation to write down passwords
on Post-It notes stuck to their monitors or hidden under their
keyboards. Instead, they should choose passwords that they will be
able to remember – not an easy task given the complexity required
of strong, effective passwords.

There are always extraneous circumstances where we must write down
passwords. This is not recommended, but if it must be done, it
should be done with forethought, not haphazardly. The extreme
example of too many passwords is contract system administrators,
who have multiple clients and machines. For these people, the only
advice is to write down the phrases or some sort of related
thought to jog your memory and put it on a piece of paper carried
on your person. Maybe photocopy that and leave that stored in a
safe place at home. Never put it on a Post-It. Never store it
online. An obscured hint might be okay, but never the actual
password or even an encrypted version.

Changing & Storing Passwords and PINs

In order to ensure their ongoing effectiveness, passwords should
be changed on a regular basis. Changing passwords securely is
fairly simple. Windows passwords are changed through the Control
Panel and in UNIX, the ‘passwd’ command generally does the trick.
A good rule of thumb is to change passwords as close to the actual
account as possible. For example, if it’s an ISP account, don’t
telnet through three other machines to change that password. If
it’s an office computer, users should be on that computer and not
on a co-worker’s when changing it. Don’t let anybody watch while
typing the old and new passwords. If at all possible, the password
should be changed over a secure connection like a secure shell
(SSH).

How often one should change passwords really depends on the
account. Online financial accounts should be changed every month
or two. Corporate network passwords should be changed every 3-4
months. A recent 2600 article recommended considering the
“sensitivity of the resources which you are trying to protect” and
suggested “enforcing password changes somewhere between once per
fiscal year and once per fiscal quarter” (Thomas). Just use good
judgment and don’t be lazy. Changing a password is relatively
quick and painless compared to the irritating and expensive
process of combating identity theft.

Tips for Organizations and Network Administrators

Managers and administrators can enhance the security of their
networks by setting strong password policies. Password
requirements should be built into organizational security
policies. Network administrators should institute by regular
changes/updates of passwords. They should also regularly remind
users of how easy it is for hackers to get their passwords through
social engineering and online attacks. New users should be taught
about good password practices. Providing intranet resources on
network security and password security can also be helpful.
Finally, the organization’s password policy should be integrated
into the security policy, and all readers should be made to read
the policy and sign-off on it.

Systems administrators should implement safeguards to ensure that
people on their systems are using adequately strong passwords.
They should set password expiration dates on all programs being
run on the organization’s systems. Keep a password history to
prevent reuse, and lock of accounts after 3-5 password attempts.
Keep the number of people in the organization who have these
passwords as small as possible. The organization should also use
newer versions of OSs that have more secure password files and
authentication protocols. Keep your individual account passwords
updated as well. Finally, when installing new systems, make sure
default passwords are changed immediately.

New Year’s Resolution

Obviously, passwords are just one piece of the puzzle. Other
pieces are general user education, good physical security,
plugging network holes, and installing strong firewalls. These
provide much more global protection in the controlled corporate
environment than passwords alone, but in areas where the only
method of control users have is a PIN or password, the best thing
we can do is be aware of security risks and keep up with their
password controls.

References

Armstrong, Del and Simonson, John: “Password Guessing” and
“Password Sniffing,” An Intro to Computer Security, School of
Engineering & Applied Sciences, University of Rochester, Oct. 25,
1996.
http://www.seas.rochester.edu:8080/CNG/docs/Security/security.html

Belgers, Walter: “UNIX Password Security,” JANET-CERT, Dec. 6,
1993.
http://www.ja.net/CERT/Belgers/UNIX-password-security.html

Cliff, A.: “Password Crackers - Ensuring the Security of Your
Password”, Security Focus, Feb. 19, 2001.
http://www.securityfocus.com/infocus/1192

Cons, Lionel: CERN Security Handbook (Practical computer security
for CERN users), Version 1.2, 12 December 1996.
http://consult.cern.ch/writeups/security/security_3.html#SEC7

Donovan, Craig: “Strong Passwords,” SANS Institute, June 2, 2000.
http://www.sans.org/infosecFAQ/policy/password.htm

Garfinkel, Simson and Spafford, Gene: Practical UNIX Security,
O’Reilly & Associates, Inc. Sebastopol, CA, 1991 & 1996.

MacGregor, Tina: “Password Auditing and Password Filtering to
Improve Network Security”, SANS Institute, May 13, 2001.
http://rr.sans.org/authentic/improve.php

“Password Security: A Guide for Students, Faculty, and Staff of
the University of Michigan,” University of Michigan, Information
Technology Division, Reference R1192, Revised April 1997.
http://www.umich.edu/~policies/pw-security.html

Russell, Deborah and Gangemi Sr., G.T.: Computer Security Basics,
O’Reilly & Associates, Inc. Sebastopol, CA, 1991.

Thomas, Stephen: “Popular Myths on Password Authentication,” 2600,
Summer 2001
http://www.2600.com

Visser, Joe: “On NT Password Security,” Open Solution Providers,
1997.
http://www.osp.nl/infobase/ntpass.html

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