trojan horse

n. large wooden horse which contained Greek warriors who surprise attacked the Trojans (Classical Mythology); something which is ostensibly good but brings harm; computer program which looks useful but contains a harmful code

The Trojan Horse is part of the Trojan War, as told in Virgil's Latin epic poem The Aeneid. The events of this, take place after Homer's Iliad, and before Homer's The Odyssey.
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Noun
1. a large hollow wooden figure of a horse (filled with Greek soldiers) left by the Greeks outside Troy during the Trojan War
(synonym) Wooden Horse
(hypernym) figure
(classification) Greece, Hellenic Republic, Ellas

Noun
1. a subversive group that supports the enemy and engages in espionage or sabotage; an enemy in your midst
(synonym) fifth column
(hypernym) unit, social unit
(member-meronym) fifth columnist, saboteur

Noun
1. a program that appears desirable but actually contains something harmful; "the contents of a trojan can be a virus or a worm"; "when he downloaded the free game it turned out to be a trojan horse"
(synonym) trojan
(hypernym) malevolent program

[Greek heroic] When the Greeks had lain siege to Troy for ten years, without results, they pretended to retreat. They left behind a huge wooden horse, in which a number of Greek heroes, among whom Odysseus, had hidden themselves. The spy Sinon convinced the Trojans, despite the warnings of Laocoon, to move the horse inside the city as a war trophy. In the following night, the Greeks left the wooden horse and attacked the unsuspecting and celebrating Trojans, and finally conquered Troy.

<application, security> (Coined by MIT-hacker-turned-NSA-spook Dan Edwards) A malicious, security-breaking program that is disguised as something benign, such as a directory lister, archiver, game, or (in one notorious 1990 case on the Mac) a program to find and destroy viruses! A Trojan horse is similar to a back door.
See also RFC 1135, worm, phage, mockingbird.
[Jargon File]
(1995-03-21)