ScamScan Dictionary

Definition of 'Trojan'

A 'trojan' (or 'trojan horse') program is one that pretends to do something useful (free software or screensavers, for example) whilst secretly doing something bad (like installing malware). The term comes from the myth about the Trojan war, where the Greeks built a giant wooden horse and hid soldiers inside it. The Trojans took the horse inside their city, and once night fell the Greek warriors came out of the horse and captured the city.

Although some trojan programs are deliberately malicious, others are used to generate income (from adverts displayed by any adware also installed) for otherwise 'free' software. There is normally a clause in the EULA of the software warning the user that a particular piece of adware is going to be installed (although it will probably not be described as 'adware'!)

Although anti-spyware software may be able to detect and remove the malware installed by a trojan program, this may stop the 'useful' part of the trojan from working at all - it's then up to the user to decide whether the value of the software is greater than the price of the adware/spyware being installed.