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ITL Bulletin for December 2005
ITL Bulletin for December 2005
ITL Bulletin for December 2005
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Forwarded from: Elizabeth Lennon
PREVENTING AND HANDLING MALWARE INCIDENTS: HOW
TO PROTECT INFORMATION TECHNOLOGY SYSTEMS FROM
MALICIOUS CODE AND SOFTWARE
Shirley Radack, Editor
Computer Security Division
Information Technology Laboratory
National Institute of Standards and Technology
U.S. Department of Commerce
The term malware is used to describe malicious code and malicious
software that are covertly inserted into an information technology
(IT) system to compromise the confidentiality, integrity, or
availability of the data, applications, or operating system, or to
annoy or disrupt the system's owner. Malware incidents are a
significant external threat to the security of many IT systems, often
causing widespread damage and disruption, and forcing users and
organizations to carry out extensive, costly efforts to restore system
Malware includes five categories of inserted programs: viruses,
worms, Trojan horses, malicious mobile code, and blended attacks.
Viruses and worms are usually designed to carry out their functions
without the user's knowledge. Blended attacks use a combination of
techniques to insert malicious programs. Malware also includes other
attacker tools such as backdoors, rootkits, and keystroke loggers, and
tracking cookies which are used as spyware. Spyware, when inserted
into a user's system, threatens personal privacy and enables the
attacker to monitor personal activities and to carry out financial
Guide to Malware Incident Handling and Prevention: Recommendations of
the National Institute of Standards and Technology
NIST's Information Technology Laboratory recently published NIST
Special Publication (SP) 800-83, Guide to Malware Incident Handling
and Prevention: Recommendations of the National Institute of Standards
and Technology. The guide assists organizations and users in planning
and implementing security programs to prevent potential malware
incidents and to limit damage from unforeseen incidents that might
Written by Peter Mell of NIST and Karen Kent and Joseph Nusbaum of
Booz Allen Hamilton, NIST SP 800-83 discusses the different types of
malware and recommends prevention and incident handling techniques.
The appendices provide additional resources on malware prevention and
handling methods, and include detailed techniques and scenarios. A
glossary of the many specialized terms used in the guide, a list of
acronyms, and an extensive reference list of print and online
resources are also provided. The publication is available in
electronic format from NIST's website:
Malware: What it is
Malware includes the following major categories of malicious code and
* Viruses are self-replicating codes that insert copies of the virus
into host programs or data files. Viruses often result from user
interactions, such as opening a file or running a program, and
o Compiled viruses that are executed by an operating system. These
include file infector viruses, which attach themselves to executable
programs; boot sector viruses, which infect the master boot records of
hard drives or the boot sectors of removable media; and multipartite
viruses, which combine the characteristics of file infector and boot
o Interpreted viruses that are executed by an application. These
include macro viruses that take advantage of the capabilities of the
macro programming language to infect application documents and
document templates; and scripting viruses that infect scripts and are
understood by scripting languages processed by services on the
* Worms are self-replicating, self-contained programs that usually
perform without user intervention. Worms create fully functional
copies of themselves, and they do not require a host program to infect
a system. Attackers often insert worms because they can potentially
infect many more systems in a short period of time than a virus can.
o Network service worms that take advantage of vulnerabilities in
network services to propagate and infect other systems.
o Mass mailing worms that are similar to e-mail-borne viruses but are
self-contained, rather than infecting an existing file.
* Trojan horses are self-contained, non-replicating programs that
appear to be benign, but that actually have a hidden malicious
purpose. Trojan horses either replace existing files with malicious
versions or add new malicious files to systems. They often deliver
other attacker tools to systems.
* Malicious mobile code is software with malicious intent that is
transmitted from a remote system to a local system. The inserted
programs are executed on the local system, usually without the user's
explicit instruction. Programs delivered in this way can be used by
many different operating systems and applications, such as web
browsers and e-mail clients. Although the mobile code may be benign,
attackers use it to transmit viruses, worms, and Trojan horses to the
user's workstation. Malicious mobile code does not infect files or
attempt to propagate itself, but exploits vulnerabilities by taking
advantage of the default privileges granted to mobile code.
Languages used for malicious mobile code include Java, ActiveX,
* Blended attacks use multiple methods of infection or transmission. A
blended attack could combine the propagation methods of viruses and
* Tracking cookies are persistent cookies that are accessed by many
websites, allowing a third party to create a profile of a user's
behavior. Tracking cookies are often used in conjunction with web
bugs, which are tiny graphics on websites and which are referenced
within the HTML content of a web page or e-mail. The purpose of the
graphic is to collect information about the user viewing the content.
* Attacker tools might be delivered to a system as part of a malware
infection or other system compromises. These tools allow attackers to
have unauthorized access to or use of infected systems and their data,
or to launch additional attacks. Popular types of attacker tools
o Backdoors are malicious programs that listen for commands on a
certain TCP or UDP port. Most backdoors allow an attacker to perform a
certain set of actions on a system, such as acquiring passwords or
executing arbitrary commands. Backdoors include zombies (also known
as bots), which are installed on a system to cause it to attack other
systems, and remote administration tools, which are installed on a
system to enable a remote attacker to gain access to the system's
functions and data.
o Keystroke loggers monitor and record keyboard use. Some require the
attacker to retrieve the data from the system, while other loggers
actively transfer the data to another system through e-mail, file
transfer, or other means.
o Rootkits are collections of files that are installed on a system to
alter its standard functionality in a malicious and stealthy way. A
rootkit can make many changes to a system to hide the rootkit=92s
existence, making it very difficult for the user to determine that the
rootkit is present and to identify what changes have been made.
o Web browser plug-ins provide a way for certain types of content to
be displayed or executed through a web browser. Attackers often create
malicious web browser plug-ins that act as spyware and monitor the use
of the browser.
o E-mail generators are programs that can be used to create and send
large quantities of e-mail, such as malware, spyware, and spam, to
other systems without the user's permission or knowledge.
o Attacker toolkits include several different types of utilities and
scripts that can be used to probe and attack systems, such as packet
sniffers, port scanners, vulnerability scanners, password crackers,
remote login programs, and attack programs and scripts.
* Common non-malware threats associated with malware include phishing,
which uses computer-based means to trick users into revealing
financial information and other sensitive data. Phishing attacks
frequently place malware or attacker tools on systems. Virus hoaxes,
which are false warning of new malware attacks, are another common
Recommendations for Preventing Malware Incidents
Organizations should protect their information and information systems
from malware through their ongoing IT security planning, management,
and implementation activities. NIST recommends that organizations
take the following actions to prevent malware incidents and to respond
effectively and efficiently to any attacks that might occur.
Develop and implement an approach to malware incident prevention,
based on the attack methods that are most likely to be used, both
currently and in the near future. Choose prevention techniques that
are appropriate to the computing environment and system, and provide
for policy statements, awareness programs for users and IT staff, and
vulnerability and threat mitigation efforts.
Ensure that policies support the prevention of malware incidents and
provide for user and IT staff awareness, vulnerability mitigation, and
security tool deployment and configuration. Malware prevention should
be stated clearly in policies, which should be as general as possible
to allow for flexibility in implementation and to reduce the need for
frequent updates. At the same time, policy statements should be
specific enough to make their intent and scope clear and to achieve
consistent and effective results. Policies should include provisions
that are applicable to remote workers, both those using systems
controlled by the organization and those using systems outside of the
organization=92s control such as contractor computers, home computers,
computers of business partners, and mobile devices.
Incorporate malware incident prevention and handling into awareness
programs and provide guidance and training to users. Users should be
alerted to the ways that malware spreads, the risks that malware
poses, the inability of technical controls to prevent all incidents,
and the role of users in preventing incidents. Users should be aware
of policies and procedures for incident handling, including how to
detect malware on a computer, how to report suspected infections, and
what can be done to assist the incident handlers.
Establish capabilities to mitigate vulnerabilities and to help prevent
malware incidents through documented policy, technical processes, and
procedures. Appropriate techniques or combinations of techniques
should be used for patch management, application of security
configuration guides and checklists, and host protection to address
Establish threat mitigation capabilities to assist in containing
malware incidents by detecting and stopping malware before it can
affect systems. NIST strongly recommends that organizations install
antivirus software on all systems when such software is available.
Other technical controls that can be used are intrusion prevention
systems, firewalls, routers, and certain application configuration
Establish a robust incident response process capability that addresses
malware incident handling through preparation, detection and analysis,
containment/eradication/recovery, and post-incident activities.
o Preparation. Develop malware-specific incident handling policies and
procedures. Regularly conduct malware-oriented training and exercises;
designate a few individuals or a small team to be responsible for
coordinating the organization's responses to malware incidents.
Establish several communication mechanisms so that coordination among
incident handlers, technical staff, management, and users can be
sustained if an attack occurs.
o Detection and Analysis. Monitor malware advisories and alerts
produced by technical controls, such as antivirus software, spyware
detection and removal utilities, and intrusion detection systems, to
identify impending malware incidents. Review malware incident data
from primary sources such as user reports, IT staff reports, and
technical controls to identify malware-related activity. Construct
trusted toolkits on removable media that contain up-to-date tools for
identifying malware, listing currently running processes and
performing other analysis actions. Establish a set of prioritization
criteria that identify the appropriate level of response for various
o Containment. Decide who has the authority to make major containment
decisions, when actions are appropriate, and the methods of
containment that will be employed. Early containment can help stop the
spread of malware and prevent further damage to systems. Strategies
and procedures for making containment-related decisions should reflect
the level of risk acceptable to the organization.
Provide users with instructions on how to identify infections and what
measures to take if a system is infected, but do not rely primarily on
users for containing malware incidents. Use updated antivirus software
and other security tools to contain incidents. Submit copies of
unknown malware to security software vendors for analysis and contact
trusted parties, such as incident response organizations and antivirus
vendors, when guidance is needed on handling new threats.
Be prepared to shut down or block services such as e-mail or Internet
access to contain a malware incident and understand the consequences
of doing so. Be prepared to respond to problems caused by other
organizations disabling their own services in response to a malware
incident. Identify those hosts infected by malware, considering users
who have remote access to systems and mobile users.
o Eradication. Be prepared to use combinations of eradication
techniques simultaneously for different situations to remove malware
from infected systems. Support awareness activities to inform users
about eradication and recovery efforts.
o Recovery. Restore the functionality and data of infected systems and
lift temporary containment measures. Consider possible worst-case
scenarios and determine how recovery should be performed, including
rebuilding compromised systems from scratch or known good backups.
Determine when to remove temporary containment measures, such as
suspension of services or connectivity. Containment measures should
be kept in place until the number of infected systems and systems
vulnerable to infection is sufficiently low that subsequent incidents
should be of little consequence. The incident response team should
assess the risks of restoring services or connectivity and report to
organization managers, who are responsible for assessing the business
impact of maintaining the containment measures and for determining
actions to be taken concerning containment.
o Post-Incident Activity. Conduct an assessment of lessons learned
after major malware incidents to prevent similar future incidents.
Identify needed changes to security policy, software configurations,
and the implementation of malware detection and prevention controls.
Establish malware incident prevention and handling capabilities that
address current and short-term future threats and that are robust and
flexible. Maintain awareness on the latest threats and the security
controls that are available to combat each threat. Plan and implement
appropriate controls, emphasizing the prevention of malicious
The use of malware, spyware, phishing attacks, and other attempts to
collect personal information are expected to lead to future identity
theft and financial fraud. Demands for better protection should drive
the development of more robust spyware detection and removal
utilities, and more effective antivirus software. But there is always
a concern that better technical controls could make attackers even
more resourceful and innovative in avoiding automated detection and
taking advantage of the trust of users. Other future threats are
viruses and worms that could attack PDA devices and cell phones, or
that could use these devices as malware carriers. Organizations must
always be aware of the latest threats and should be prepared to
implement appropriate security controls to protect their IT systems.
The following Special Publications (SPs) provide help to organizations
in planning and implementing effective security controls. These
publications are available in electronic format from the NIST Computer
Security Resource Center at http://csrc.nist.gov/publications.
NIST SP 800-28, Guidelines on Active Content and Mobile Code,
discusses the security risks and security controls associated with the
technology of active content.
NIST SP 800-31, Intrusion Detection Systems (IDS), provides
information on installing and using intrusion detection systems.
NIST SP 800-40, Version 2, Creating a Patch and Vulnerability
Management Program, helps organizations establish patch and
vulnerability management programs to protect IT systems from the
exploitation of vulnerabilities.
NIST SP 800-42, Guideline on Network Security Testing, describes
available security testing techniques, their strengths and weaknesses,
and the recommended frequencies for testing as well as strategies for
deploying network security testing.
NIST SP 800-45, Guidelines on Electronic Mail Security, describes
secure practices for the installation, configuration, and maintenance
of mail servers and clients.
NIST SP 800-53, Recommended Security Controls for Federal Information
Systems, helps organizations to identify, select, and implement needed
controls, including malware protection mechanisms for workstations,
servers, mobile computing devices, firewalls, e-mail servers, and
remote access servers.
NIST SP 800-61, Computer Security Incident Handling Guide, describes
the four phases of the incident response process -- preparation,
detection and analysis, containment/eradication/recovery, and
Any mention of commercial products or reference to commercial
organizations is for information only; it does not imply
recommendation or endorsement by NIST nor does it imply that the
products mentioned are necessarily the best available for the purpose.
Elizabeth B. Lennon
Information Technology Laboratory
National Institute of Standards and Technology
100 Bureau Drive, Stop 8900
Gaithersburg, MD 20899-8900
Telephone (301) 975-2832
Fax (301) 975-2378
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