A program that appears legitimate but which performs some harmful activity when it is run. It may be used to locate password information, or make the system more vulnerable to future entry, or simply destroy programs or data on the hard disk drive. A trojan is similar to a virus except that it does not replicate itself. It stays in the computer doing its damage or allowing somebody from a remote site to take control of the computer. Trojans often sneak in attached to a free game.
