In computers, a Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data in such a way that it can get control and do its chosen form of damage, such as ruining the on your hark disk. In one celebrated case, a Trojan horse was a program that was supposed to find and destroy computer es. A Trojan horse may be widely redistributed as part of a computer virus.
The term comes from Greek mythology about the Trojan War, as told in the AeneidOdyssey by Homer. According to legend, the Greeks presented the citizens of Troy with a large wooden horse in which they had secretly hidden their warriors. During the night, the warriors emerged from the wooden horse and overran the city.