TROJAN

Trojan horses are a huge security threat. A Trojan is a program that enters your computer undetected, giving the attacker who planted the Trojan unrestricted access to the data stored on your computer. Trojans can transmit credit card information and other confidential data in the background. Trojans are often not caught by virus scanning engines, because these are focused on viruses, not Trojans. Catching such threats would require the use of a Trojan scanner (a.k.a Trojan cleaner, Trojan remover, anti-Trojan).