This is not a benefit of a firewall. Most firewalls are limited when it comes to preventing the spread of viruses.
This question is testing your knowledge of Malware and Firewalls. The keywords within the questions are 'usually' and 'virus'. Once again to come up with the correct answer, you must stay within the context of the question and really ask yourself which of the 4 choices is NOT usually done by a firewall.
Some of the latest Appliances such as Unified Threat Management (UTM) devices does have the ability to do virus scanning but most first and second generation firewalls would not have such ability. Remember, the questions is not asking about all possible scenarios that could exist but only about which of the 4 choices presented is the BEST.
For the exam you must know your general classes of Malware. There are generally four major classes of malicious code that fall under the general definition of malware:
1. Virus: Parasitic code that requires human action or insertion, or which attaches itself to another program to facilitate replication and distribution. Virus-infected containers can range from e-mail, documents, and data file macros to boot sectors, partitions, and memory fobs. Viruses were the first iteration of malware and were typically transferred by floppy disks (also known as ''sneakernet'') and injected into memory when the disk was accessed or infected files were transferred from system to system.
2. Worm: Self-propagating code that exploits system or application vulnerabilities to replicate. Once on a system, it may execute embedded routines to alter, destroy, or monitor the system on which it is running, then move on to the next system. A worm is effectively a virus that does not require human interaction or other programs to infect systems.
3. Trojan Horse: Named after the Trojan horse of Greek mythology (and serving a very similar function), a Trojan horse is a general term referring to programs that appear desirable, but actually contain something harmful. A Trojan horse purports to do one thing that the user wants while secretly performing other potentially malicious actions. For example, a user may download a game file, install it, and begin playing the game. Unbeknownst to the user, the application may also install a virus, launch a worm, or install a utility allowing an attacker to gain unauthorized access to the system remotely, all without the user's knowledge.
4. Spyware: Prior to its use in malicious activity, spyware was typically a hidden application injected through poor browser security by companies seeking to gain more information about a user's Internet activity. Today, those methods are used to deploy other malware, collect private data, send advertising or commercial messages to a system, or monitor system input, such as keystrokes or mouse clicks.
The following answers are incorrect:
reduces the risks of external threats from malicious hackers. This is incorrect because a firewall can reduce the risks of external threats from malicious hackers.
reduces the threat level on internal system. This is incorrect because a firewall can reduce the threat level on internal system.
allows centralized management and control of services. This is incorrect because a firewall can allow centralize management and control of services.
Reference(s) used for this question:
Hernandez CISSP
, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 3989-4009). Auerbach Publications. Kindle Edition.
