Trojan horses

A Trojan horse, or Trojan is malware that is defined by its delivery method. Through the use of social engineering, or some other method, the code is installed on a system by a valid user of the system and like the original Trojan horse there is something more than advertised within the software. Trojans, unlike worms or viruses are generally non-self-replicating. The most common payload of a Trojan is the setting up of a “backdoor” control mechanism to the system that it is installed on.