Trojan horse. Conceptual computer artwork of a wooden horse on wheels entering through city gates made from computer parts. This could represent a type of malicious computer program known as a trojan. A trojan is a destructive program disguised as a benign application. It can cause major problems such as deletion of data but, unlike a computer virus, is unable to replicate. Ther term comes from a story in Homer's Iliad where a giant wooden horse was given to the Trojans as a peace offering by the Greeks. The horse's hollow interior contained Greek soldiers who opened the city gates and allowed the Greeks to take Troy.