Computer virus

A computer virus is a piece of unauthorized software added to a computer which automatically spreads itself to other computers. Some viruses do malicious things, such as erasing files or copying sensitive information (like passwords and credit card numbers).

Discussion of the virus problem is sometimes hampered by the terminology used by purists, who distinguish between such varieties as "worm", "Trojan Horse", etc. But the generic term for unwanted software that infects your computer is "virus".