Trojan

A Trojan is known as a backdoor program that may or may not leave damaging items on a computer. Technically speaking, it is not an official virus. Like a virus, it can self-replicate, but actually depends on exploitation of the unknowing end user. In the case of a program such as malware or spyware being dropped, a Trojan is known for initiating viruses. Most of the time, a Trojan horse inflicts damage because of action taken by a user. It is very clever in methods of deception, often posing as interesting or useful content. A Trojan may wait for a user in an email message or a legitimate website. The infected program may then arrive via email, instant message, or FTP client. In some cases, it can be installed from a CD or floppy disk. Though rare, an experienced writer can sit down and manually install a Trojan directly on someone else’s computer.