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).
Process of transmission
There are three main ways a virus is transmitted.
- Automatic replication. When an infected program is run, the virus also runs, searching the host computer for other programs to infect.
- By email. When email software is configured to run scripts or programs attached to messages, the virus asks the email software to send it to recipients in the user's address book.
- Misleading advertising. A "Trojan Horse" is a program which seems useful, but contains a virus (or other malware). The main program may or not perform as advertised, but the distributor knows it is infected. A Trojan Horse carried virus typically does not replicate itself but is spread when the user copies the program.
A virus which infects networks is called a "worm".
Anti-virus tactics
Configuring email software so that it never runs attached programs or embedded scripts is an easy way to stop email-transmitted viruses. This should be the default setting, especially for corporate systems.
Virus scanning software is available from Norton, Symantec and other companies. This software detects known viruses and removes them from infected programs, messages, and systems.
Computer users should also be aware that free games and other such scripts available on the Internet can be risky to use. Reputable software companies go to great lengths to ensure virus-free software, so it is wise to stick with these whenever possible. Using a designated computer (or virtual system) is a safer way to experiment with such higher-risk internet services.
Terminology
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 a common term for unwanted software that infects computers is "virus". A more technically correct term is "malware."