The word virus is often used in refference to all formes of harmful software, when in reality there are many different "species" of viruses.

True viruses infect computers by coping themselves. They spread through USB drives, floppy disks, and any other form of exicutable coad.

Trojan horses appear harmless when you download them, but in time they are accesed by a hacker and unleash a volley of terror. Some of the tasks trojans perform are data theft, keystroke logging, and downloading othet viruses.

Worms are self-replicating programs that use networks to send themselves to other computers. Worms are notorious for causing computer dammage wherever they appear.computer-virus1.JPG