Definitions for "Trojan Horses"
are impostor files that claim to be something desirable but are actually malicious. Trojan horse programs do not replicate themselves. They contain malicious code that causes loss, or even theft, of data when triggered
A Trojan horse is a program that performs unauthorized actions within a system, which are usually malicious. They can erase files, reformat a disk, or display certain messages. It is a program looks as if it's legitimate but is actually malicious. Trojans are most effective at gaining backdoor access into a system. It will not infect other files, so cleaning of the system is not necessary. To get rid of a Trojan, you just need to delete the Trojan program. Trojans do not replicate or make copies of themselves, however they are often combined with viruses and worms which do.
Trojan horses slip into an individual's system and run without the user's knowledge. They can have many functions. For example, some use a computer's modem to dial long-distance, generating huge phone bills for the computer owner. Unlike viruses and worms, Trojan horses do not make copies of themselves.