A computer virus is generally a small piece of code which will replicate itself and try to hide on a computer disguised as a file or attached to another program file. Computers on which a virus successfully hides itself is referred to as infected. The computer virus almost always has a harmful purpose such as filling up hard disk space, making the computer unusable, logging keystrokes made by the user, corrupting data or even displaying a message or picture on the computer screen.

Computer virus scanners are always working to increase their databases of known virus definitions so as to scan for them and quarantine the infected files. Once a computer virus has been quarantined it is prevented from carrying out it’s “payload” whatever it may have been. There have been many well publicized computer viruses in the past and they are often designed to exploit small, little-known vulnerabilities in computer operating systems. Some viruses can even attach themselves to your email software and email themselves to all of the people in your address book thereby spreading even further.