virus

security (By analogy with biological viruses, via SF) A

program or piece of code written by a cracker that "infects"

one or more other programs by embedding a copy of itself in

them, so that they become Trojan horses. When these

programs are executed, the embedded virus is executed too,

thus propagating the "infection". This normally happens

invisibly to the user.

A virus has an "engine" - code that enables it to propagate

and optionally a "payload" - what it does apart from

propagating. It needs a "host" - the particular hardware and

software environment on which it can run and a "trigger" - the

event that starts it running.

Unlike a worm, a virus cannot infect other computers without

assistance. It is propagated by vectors such as humans

trading programs with their friends (see SEX). The virus

may do nothing but propagate itself and then allow the program

to run normally. Usually, however, after propagating silently

for a while, it starts doing things like writing "cute"

messages on the terminal or playing strange tricks with the

display (some viruses include display hacks). Viruses

written by particularly antisocial crackers may do

irreversible damage, like deleting files.

By the 1990s, viruses had become a serious problem, especially

among IBM PC and Macintosh users (the lack of security on

these machines enables viruses to spread easily, even

infecting the operating system). The production of special

antivirus software has become an industry, and a number of

exaggerated media reports have caused outbreaks of near

hysteria among users. Many lusers tend to blame

*everything* that doesn't work as they had expected on virus

attacks. Accordingly, this sense of "virus" has passed into

popular usage where it is often incorrectly used for a worm

or Trojan horse.

See boot virus, phage. Compare back door. See also

Unix conspiracy.

[Jargon File]

(2003-06-20)