The final type of malware we will discuss in our ongoing series is a Trojan. The term “Trojan horse” comes from Greek mythology in a story from the Trojan War about the trickery that the Greeks performed to enter the independent city of Troy and win the war. Metaphorically, a “Trojan horse” has come to mean any trick that causes a target to invite a foe into a securely protected place. In computer terminology a Trojan is simply a malicious computer program that tricks users into willingly running it.
Conceptually, a Trojan and virus are very similar with the main difference being that a virus typically infects a legitimate program whereas a Trojan is an illegitimate program whose only purpose is to infect a computer. The Trojan usually masquerades as a legitimate file that is often attached to an email or downloaded via social engineering from a malicious website. Once the file has been downloaded and is executed, it acts like a virus to infect the computer. After infecting the computer, the malicious software then does whatever it is designed to do such as steal passwords, install spyware or delete files.