computer virusesAntivirus programs have developed in parallel with the evolution of viruses. As new technologies create viruses, is complicated and mathematical tools used in the development of anti-virus.

The first anti-virus algorithms were based on a comparison with the standard. This is a program in which the virus is determined by the classical core of a mask. The meaning of the algorithm is to use statistical methods. The mask should be, on the one hand, the small size of the file to a manageable size, and on the other – big enough to avoid false positives (when “a” is perceived as “foreign”, and vice versa).

The first anti-virus software, built on this principle (called crawlers, polyphagous), knew a number of viruses and know how to treat them. These programs were created in the following way: the developer, get the code of the virus (the virus code was initially static), was on the code unique mask (the sequence of bytes 10-15) and has made it into the database antivirus software. Antivirus program scans the files and, if found this sequence of bytes, it is concluded that the file is infected. This sequence (signature) was chosen so that it is unique and is not found in the normal data set. Continue reading