What is a Trojan horse computer attack?

Definition: A Trojan horse is a self-contained, malicious program, that is, it is a bit of software code that does something bad to your computer. It does not replicate itself (as a worm would), nor does it infect other files (as a virus would). However, Trojans are often grouped with viruses and worms, because they can have the same type of damaging effect.

Many of the early Trojans were used to launch Distributed Denial of Service (DDoS) attacks, such as those that hit Yahoo and eBay in late 1999. Today, Trojans are more often used to gain backdoor access – remote and surreptitious access – to the computer.

There are several different types of Trojans, including Remote Access Trojans (RATs), backdoor Trojans (backdoors), IRC Trojans (IRCbots), and keyloggers. Many of these different features can be used in a single Trojan. For example, a keylogger that also functions as a backdoor can be commonly disguised as a game hacker. IRC Trojans are often combined with backdoors and RATs to create collections of infected computers known as botnets.

Also Known As: Trojan Horse