Protecting Systems with Antivirus Software

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If you’re planning on taking the Security+ exam, you should have a basic understanding of antivirus software and how it protects systems.

For example, can you answer this question?

Q. You manage a group of computers in an isolated network without Internet access. You need to update the antivirus definitions manually on these computers. Which of the following choices is the MOST important concern?

A. Running a full scan of the systems before installing the new definitions

B. Running a full scan of the systems after installing the new definitions

C. Ensuring the definition file hash is equal to the hash on the antivirus vendor’s website

D. Ensuring the update includes all signature definitions

More, do you know why the correct answer is correct and the incorrect answers are incorrect? Answer and explanation at end of this post.

Malware is a significant threat for any organization. Administrators commonly implement layered security, or a defense-in-depth plan, to protect against malware.

Using Antivirus Software

Anti-malware software provides protection against many types of malware. You’ll often hear the term antivirus software indicating it only protects against viruses. However, the lines have blurred. Viruses aren’t the only threats. Attackers have changed their methodologies using different types of malware, and antivirus software vendors have adapted by including methods to detect and block these new threats. Most antivirus software detects, blocks, and removes several different types of malware, such as viruses, Trojans, worms, rootkits, spyware, and adware.

Antivirus software provides real-time protection and can perform both scheduled and manual scans. The real-time protection continuously monitors the system. For example, when a user visits a website, antivirus software scans the downloaded website files and attempts to block malicious code. Similarly, when a user downloads or opens a file, antivirus software scans it before opening it. Scheduled scans occur regularly, such as once a week. If users or technicians detect suspicious activity, they can perform manual scans to check the system.

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Antivirus software detects viruses using either signature-based detection or heuristic-based detection.

Signature-Based Detection

Viruses and other malware have known patterns. Signature files (also called data definition files) define the patterns, and the antivirus software scans files for matching patterns. When the software identifies a matching pattern, it reports it as an infection and takes action, such as deleting or quarantining the file.

A quarantined virus is not harmful to the system while it is in quarantine, but it’s still available for analysis. As an example, a security professional could release a quarantined virus into an unprotected but isolated virtual environment for research and study.

Antivirus Software

Malware developers constantly release new viruses, so it’s important to update signature definition files regularly. Most antivirus software includes the ability to automate the process of checking and downloading updated signature definition files. They typically check for updates several times a day.

It’s also possible to download and install signature files manually. Administrators do this when updating systems that do not have Internet access. When doing so, it’s important for administrators to ensure the signature file has not lost data integrity. They do so by comparing the hash of the signature file posted on the antivirus vendor’s website with the hash of the downloaded file.

To see an example of how to compare hashes, check out the Creating and Comparing Hashes Lab. You can access the online exercises at http://gcgapremium.com/labs/.

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Heuristic-Based Detection

Some antivirus software includes heuristic-based detection. Heuristic-based detection attempts to detect viruses that were previously unknown and do not have signatures. This includes zero-day exploits.

Heuristic-based analysis runs questionable code in a sandbox or virtualized environment specifically designed to protect the live environment, while it observes its behavior. Most viruses engage in viral activities—actions that can be harmful, but are rarely performed by legitimate programs. The heuristic-based analysis detects these viral activities.

As an example, polymorphic malware adds variations to files when it creates copies. It’s highly unusual for any application to add variations in files like this, and heuristic methods are often successful at detecting polymorphic malware.

Remember this

Antivirus software detects and removes malware, such as viruses, Trojans, and worms. Signature-based antivirus software detects known malware based on signature definitions. Heuristic-based software detects previously unknown malware based on behavior.

File Integrity Checker and Antivirus Scanners

Some antivirus scanners use file integrity checkers to detect modified system files. A file integrity checker calculates hashes on system files as a baseline. It then periodically recalculates the hashes on these files and compares them with the hashes in the baseline. If the hashes are ever different, it indicates the system files have been modified. When an antivirus scanner detects a modified file, it sends an alert. Many times these alerts can detect rootkit infections.

When searching for rootkits, antivirus scanners also have the ability to inspect RAM.


Security+ Practice Test Questions

SYO-501 Practice Test Questions Now Available

SYO-401 Practice Test Questions

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 SYO-401 Practice Test Questions


INCLUDES QUESTIONS TO HELP YOU PREPARE

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Bonus - Performance Based Questions

Additional Security+ questions to help you prepare for the new performance based questions. These are included with the full bank of Security+ practice test questions and are divided into different sections. For example, you'll have access to the following links:

- Performance Based Question - Set 1

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of security to mobile devices and servers in a data center. You'll then have two questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 2

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of attacks with the name of the attack type. You'll then have five questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 3

You'll see a graphic showing a network with computers and servers separated by a firewall. The firewall is used to control traffic between the computers and users using rules within an access control list (ACL).  You'll have three questions that test your knowledge and ability to correctly identify the relevant components of the rule. The incorrect answers and explanation provide you with insight into how to correctly answer this type of question on the actual exam.

- Performance Based Question - Set 4

You'll see a graphic explaining what you might be required to do on the actual exam related to what a forensic analyst would do during an investigation. You'll then have two questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 5

You'll see a graphic explaining what you might be required to do on the actual exam to match protocols and ports. You'll then have seven questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 6

You'll see a list of security controls along with a graphic showing devices and locations within an organization, along with instructions on what you might be required to do on the actual exam to match the controls with the devices and locations. You'll then have four questions that test your knowledge and ability to correctly answer the questions. This question also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 7

You'll see a list of authentication methods and authentication factors along with instructions on what you might be required to do on the actual exam to match the authentication methods with the authentication factors. You'll then have six questions that test your knowledge and ability to correctly answer the questions. This set also includes a link to a graphic showing the end solution for the overall performance based question simulation.

- Performance Based Question - Set 8

You'll see a graphic explaining what you might be required to do on the actual exam to match different types of attacks with the name of the attack type. You'll then have five questions that test your knowledge and ability to correctly answer the questions. This is similar to Set 2 but expands on the possibilities. The set also includes a link to a page showing the end solution for the overall performance based question simulation.

New - Performance Based Question - Set 9

New questions recently added using a different testing engine. See a demo here. This set includes drag and drop and matching questions on ports.

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A random set of 20 performance-based questions using drag and drop, matching, sorting, and fill in-the blank. This set includes performance-based questions on RAID.

Get the full bank of Security+ (SYO-401) Practice Test Questions Here

Get the full bank of Security+ Practice Test Questions

Click here if you're looking for SYO-501 Practice Test Questions

Q. You manage a group of computers in an isolated network without Internet access. You need to update the antivirus definitions manually on these computers. Which of the following choices is the MOST important concern?

A. Running a full scan of the systems before installing the new definitions

B. Running a full scan of the systems after installing the new definitions

C. Ensuring the definition file hash is equal to the hash on the antivirus vendor’s website

D. Ensuring the update includes all signature definitions

Answer is C. When downloading files as important as antivirus definitions, it’s important to ensure they do not lose data integrity, and you can do so by verifying the hashes.

It’s not necessary to run a full scan either before or after installing new definitions, but the new definitions will help.

See Chapter 6 of the CompTIA Security+: Get Certified Get Ahead: SY0-401 Study Guide for information on protecting systems.

 

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