ScamScan Dictionary

Definition of 'Virus'

A computer virus is a program that tries to infect any computer it comes in contact with and spread to any other computers it can find.

In the past, computer viruses would infect existing programs on the host computer with their own code. Once infected, the virus would then start to perform whatever task the virus writer intended for it. This ranged from displaying a message to the destruction of files, but the common theme between all viruses was that they would continue to try and spread to other files and computers. Today, however, most computer viruses are smaller programs that will try and steal passwords (spyware), display adverts (adware) or just keep trying to spread.

Computer viruses used to be transferred by infected disks or files, but email has quickly become the preferred method of spreading a virus. An email virus will scan the newly infected computer for any email addresses it can find, and will send itself to all of those email addresses. Another popular method of virus infection is to create a 'trojan horse' program.

With the widespread use of anti-virus software, computer viruses have become ever more sophisticated, using a variety of techniques to avoid detection. These are quickly detected and countered by the anti-virus software vendors, and so the virus writers and anti-virus software writers are locked in a constant battle to outwit each other.