A program that allows a remote user secretly to gain control of a computer. A Trojan horse masquerades as a legitimate computer game, utility, or application. Once activated, the program positions itself to load automatically, report its presence to a server, and listen for commands. A Trojan horse often contains hidden malicious code that does something to harm the victim's computer, perhaps severely. Trojan horses often are downloaded over the Internet by unsuspecting end users. Unlike a virus, a Trojan horse cannot replicate itself.The term comes from a Greek story of the Trojan War, in which the Greeks pretended to retreat from the battlefield and left a giant wooden horse at the gates of Troy, ostensibly as a peace offering. But after the Trojans dragged the horse inside the city walls, Greek soldiers sneaked out of the hollow belly of the horse and opened the city gates to the waiting Greek army, which captured Troy. Screensavers and emoticons are common Trojan horses. See also application, emoticon, Internet, malware, utility, virus, and worm.