These viruses change their composition every time they load, making it impossible for conventional scanning software to find a known, fixed, virus signature.

Unlike virus signatures, SONAR examines the behavior of applications to decide whether they are malicious.

Signature-based Detection, on the other hand, identifies viruses and other malware by comparing the contents of a file to a dictionary of virus signatures.

Almost all of the major antivirus programs can easily be updated over the Internet, through a relatively quick download that updates the program's database of known virus signatures.

New virus signatures for MSE will be downloaded automatically on a daily basis.

The incorrect detection may be due to heuristics or to an incorrect virus signature in a database.

To identify viruses and other malware, antivirus software compares the contents of a file to a dictionary of virus signatures.

Most security software relies on virus signatures, or they employ heuristics.

Most modern antivirus programs try to find virus-patterns inside ordinary programs by scanning them for so-called virus signatures.

Such a virus signature is merely a sequence of bytes that an antivirus program looks for because it is known to be part of the virus.