What are Trojan Horses?
Trojan horses are the most destructive and dangerous species of computer viruses. Most of them are loaded at Windows Startup and are constantly in the memory of your PC. A Trojan horse is a program that does something the programmer intended, but that the user would not approve of if he knew about it. After a user installs it on their machine, the attacker can then access the user's machine remotely, via the Internet typically, and either take control of the machine or simply snoop around on it.