Trojan horse (computing)

In computing, a trojan horse (or simply trojan;^[1] often capitalized,^[2] but see below) is a kind of malware that misleads users as to its true intent by disguising itself as a normal program.

Trojans are generally spread by some form of social engineering. For example, a user may be duped into executing an email attachment disguised to appear innocuous (e.g., a routine form to be filled in), or into clicking on a fake advertisement on the Internet. Although their payload can be anything, many modern forms act as a backdoor, contacting a controller who can then have unauthorized access to the affected device.^[3] Ransomware attacks are often carried out using a trojan.

Unlike computer viruses and worms, trojans generally do not attempt to inject themselves into other files or otherwise propagate themselves.^[4]