WordNet Dictionary
Webster's 1913 Dictionary\Vi"rus\, n. [L., a slimy liquid, a poisonous liquid,
poison, stench; akin to Gr. ? poison, Skr. visha. Cf.
{Wizen}, v. i.]
1. (Med.)
(a) Contagious or poisonous matter, as of specific ulcers,
the bite of snakes, etc.; -- applied to organic
poisons.
(b) The special contagion, inappreciable to the senses and
acting in exceedingly minute quantities, by which a
disease is introduced into the organism and maintained
there.
Note: The specific virus of diseases is now regarded as a
microscopic living vegetable organism which multiplies
within the body, and, either by its own action or by
the associated development of a chemical poison, causes
the phenomena of the special disease.
2. Fig.: Any morbid corrupting quality in intellectual or
moral conditions; something that poisons the mind or the
soul; as, the virus of obscene books.
Computing Dictionary(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.
Medical DictionaryBiology Dictionary- A noncellular biological entity that can reproduce only within a host cell. Viruses consist of nucleic acid covered by protein; some animal viruses are also surrounded by membrane. Inside the infected cell, the virus uses the synthetic capability of the host to produce progeny virus.
- A computer program designed to covertly infiltrate and usually damage a computer system, either by repeatedly copying itself so that it takes up needed memory or by erasing, modifying or damaging other files.
Glossary- An infectious particle composed of a protein capsule and a nucleic acid core, which is dependent on a host organism for replication. A double-stranded DNA copy of an RNA virus genome that is integrated into the host chromosome during lysogenic infection. (See Coat protein, DNA, Genome, Host, Nucleic acid, RNA, Tumor virus)
- A noncellular biological entity that can reproduce only within a host cell. Viruses consist of nucleic acid covered by protein; some animal viruses are also surrounded by membrane. Inside the infected cell, the virus uses the synthetic capability of the host to produce progeny virus.