The most common tool used by criminals is a Trojan horse. Unlike a virus a Trojan horse does not self-replicate. A Trojan horse, or Trojan, is malicious software (malware) pretending to perform some useful function while actually installing some harmful programs creating a backdoor to your computer for some criminal to enter. The name comes from the story of the Trojan horse as referred to in the ancient Greek epic poem the Odyssey. The tale tells us that during the ten year long Trojan War the Greeks were unable to break into the city of Troy. So the Greeks built a huge wooden horse, hid a small force inside and then pretended to sail away. The Trojans seen the horse as a gift from the Greeks signifying their surrender, so they pulled the giant wooden horse into the city and celebrated. At night when the Trojans slept the force hidden inside the horse snuck out to open the gate letting in the rest of the Greek army. Just like the wooden horse the Greeks used to trick the Trojans, a criminal uses a Trojan horse program to trick you.
Just like the wooden horse the Greeks left as a gift, criminals will trick you by presenting programs that appear useful or entertaining. This method is sometimes referred to as “social engineering”. By presenting these useful gifts criminals trick you into installing a “back door” way for them to gain access to your computer without your knowledge.
For your typical user these backdoors are undetectable, usually appearing as some minor slowness. While viruses tend to embed themselves in other files a Trojan horse pretends to be other programs. Trojan horses are used to steal information, give control of your computer to another or harm a computer.
Trojan horses are typically installed when visiting a website, viewing an email message or by clicking on a pop-up window pretending to offer a useful service. In each instance it appears like you consented, even though you are unaware of the download. This is referred to as a drive-by download.
An excellent example of a currently active Trojan horse program is Trojan.Taidoor. While you are not likely to be a target of this crime it is still a good example. Trojan.Taidoor that has been changed many times since its original detection in 2008 and is still actively being distributed today .This Trojan creates a backdoor access into your computer for criminals to exploit. Originally this Trojan targeted governments and businesses. However, the most recent generation of this Trojan targets organizations directly involved in US and Taiwanese affairs. Infection methods for Trojan.Taidoor have included links in email messages and web site Java exploits. What makes this Trojan a good example is that Trojan.Taidoor gives criminals a backdoor to trespass into your computer so they can steal personal information, then transmit that information back to themselves. Since Trojan.Taidoor allows backdoor access the criminal can also install programs without your consent or knowledge.