What is a TROJAN?

A Trojan horse is full of as much trickery as the mythological Trojan horse it was named after. The Trojan horse, at first glance will appear to be useful software but will actually do damage once installed or run on your computer. Those on the receiving end of a Trojan horse are usually tricked into opening them because they appear to be receiving legitimate software or files from a legitimate source. When a Trojan horse is activated on your computer, the results can vary. Some Trojan horses are designed to be more annoying than malicious (like changing your desktop, adding silly active desktop icons) or they can cause serious damage by deleting files and destroying information on your system. Trojan horses are also known to create a backdoor on your computer that gives malicious users access to your system, possibly allowing confidential or personal information to be compromised. Unlike viruses and worms, Trojan horses do not reproduce by infecting other files nor do they self-replicate.

Web Reference
May 9, 2005