viruses

virus
computer virus
viruses

   <security> (By analogy with biological viruses, via science
   fiction) A program or piece of code, a type of {malware},
   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 other
   types of {malware} such as {worms} or {Trojan horses}.

   See {boot virus}, {phage}.  Compare {back door}.  See also
   {Unix conspiracy}.

   [{Jargon File}]

   (2003-06-20)