Trojan Horse Named after the mythological wooden horse used to sneak Odysseus and other Greek heroes into Troy, a Trojan Horse will masquerade as a legimate program but will unleash a harmful payload once installed.

Worm Computers worms are self-replicating programs that burrow into systems, seeking out vulnerabilities to exploit. The ability to spread without any user action makes them particularly dangerous.

Spyware Ever  feel  like you’re being watched? If your PC’s infected with spyware, you just might be. Even worse, spyware not only monitors your activities but can also hijack your system with redirected web searches and other annoyances.

Polymorphic To avoid detection, polymorphic malware constantly changes its own code, often using encryption with a variable key. This stealthy technique poses a problem for typical scanners.