Trojan horse (computing)
In computing, a Trojan horse (also written as trojan) is malicious software that misleads users of its true purpose. Sometimes a Trojan horse does exactly what it claims to do but it also does something else. This is because its real hidden purpose is to perform malicious actions in the background, such as allow a stranger to read and change the computer's information. In some cases the user notices, in other cases they do not. Although a Trojan horse can contain any type of harmful code, many modern forms act as a backdoor, which bypasses normal authentication or encryption in a computer.