We're not exactly sure how many computer viruses are actually attacking computer systems. Computer virus researcher Joe Wells publishes the Wild List , which describes the computer viruses thought to be infecting computers. The Virus Bulletin , an international anti-virus publication, tracks the occurrence of computer viruses. The Virus Bulletin Prevalence List provides an estimate of how likely it is to encounter a particular virus. How Viruses Work T he hype surrounding computer viruses has greatly exaggerated their abilities.
Viruses have to be written as very small programs in order to spread rapidly and escape detection.
In a practical way, that limits what a virus can do. Viruses have a method of reproduction. This ensures that more copies of the virus are spread as widely as possible. For instance, program viruses reproduce by infecting other programs. Next, viruses may have a way of evading detection by an anti-virus program.