How Antivirus Software identifies threats

Most of us are aware how Antivirus Works and updates. As ever increasing threat from virus and other malicious programs, almost every computer today comes with a pre-installed antivirus software on it. In fact, an antivirus has become one of the most essential software package for every computer. Even though every one of us have an antivirus software installed on our computers, only a few really bother to understand how it actually works and updates.

An antivirus software typically uses a variety of strategies in detecting and removing viruses, worms and other malware programs.

1. Signature-based detection – Dictionary based
2. Heuristic-based detection – Suspicious behavior based

1. Signature-based detection – Dictionary based

This is the most commonly employed method which involves searching for known patterns of virus within a given file. Every antivirus software will have a dictionary of sample malware codes called signatures in it’s database. Whenever a file is examined, the antivirus refers to the dictionary of sample codes present within it’s database and compares the same with the current file. If the piece of code within the file matches with the one in it’s dictionary then it is flagged and proper action is taken immediately so as to stop the virus from further replicating. The antivirus may choose to repair the file, quarantine or delete it permanently based on it’s potential risk.

As new viruses and malwares are created and released every day, this method of detection cannot defend against new malwares unless their samples are collected and signatures are released by the antivirus software company. Some companies may also encourage the users to upload new viruses or variants, so that the virus can be analyzed and the signature can be added to the dictionary.

More and regular the updates more secure we are.

2. Heuristic-based detection Suspicious behavior based

Heuristic-based detection involves identifying suspicious behavior from any given program which might indicate a potential risk. This approach is used by some of the sophisticated antivirus software’s to identify new malware and variants of known malware. Unlike the signature based approach, here the antivirus doesn’t attempt to identify known viruses, but instead monitors the behavior of all programs.

File emulation- This is another type of heuristic-based approach where a given program is executed in a virtual environment and the actions performed by it are logged. Based on the actions logged, the antivirus software can determine if the program is malicious or not and carry out necessary actions in order to clean the infection.

How to check your anti virus weather it does the work you haired it for?

European Institute of Computer Antivirus Research – EICAR Test makes it easy. It is a common test and most of us can perform it right now!
1. Open a notepad (New Text Document.TXT) and copy the following code exactly onto it, and save the notepad.
EICAR Test Code:
1

X5O!P%@AP[4PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*

2. Rename the file from New Text Document.TXT to mynewfile.com
3. Now run the antivirus scan on this mynewfile.com file.

If the antivirus is functioning properly on your computer, then it should generate a warning and immediately delete the file upon scanning. Otherwise find a new one.

Posted in: Articles, Genral Awareness, Securing