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.
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.
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/.
The 601 Version of the Study Guide
The CompTIA Security+: Get Certified Get Ahead: SY0-601 Study GuideEach of the eleven chapters presents topics in an easy to understand manner and includes real-world examples of security principles in action.
You’ll understand the important and relevant security topics for the Security+ exam, without being overloaded with unnecessary details. Additionally, each chapter includes a comprehensive review section to help you focus on what’s important.
Over 300 realistic practice test questions with in-depth explanations will help you test your comprehension and readiness for the exam. The book includes:
- A 75 question pre-test
- A 75 question post-test
- Practice test questions at the end of every chapter.
Each practice test question includes a detailed explanation to help you understand the content and the reasoning behind the question. You’ll be ready to take and pass the exam the first time you take it.
If you plan to pursue any of the advanced security certifications, this guide will also help you lay a solid foundation of security knowledge. Learn this material, and you’ll be a step ahead for other exams. This SY0-601 study guide is for any IT or security professional interested in advancing in their field, and a must-read for anyone striving to master the basics of IT security.
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.
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.
