The Internet brings the world to your doorstep, but it also brings hoaxters, scam artists, and phishers. Without the right protection, your computer is subject to getting sick from a virus. Viruses come in these different shapes and forms.

• E-mail virus: This kind of virus reproduces itself by going into the recipient's Address Book, taking down names, and e-mailing itself to tens or hundreds of people at once. It's important to remember that no virus can spread inside an e-mail message. Viruses travel by e-mail, but not inside messages -- they travel in files attached to e-mail messages.
• Time bomb: This is a virus that is programmed to lie quietly in wait on a computer until the appointed hour, when it "explodes" and causes damage.
• Trojan horse: This virus masquerades as one kind of program but is really another. The game you thought you downloaded turns out not to be a game at all, but a virus. Trojan horses travel on the Internet by stealth, not by reproducing themselves quickly like other viruses.
• Worm: This is a virus that quickly makes copies of itself on many computers. Worms infect a security hole in a network, and when they are inside the network, quickly copy themselves from computer to computer. Code Red, the most notorious worm, copied itself to a quarter-million computers during one day in July 2001.

Viruses slow Internet traffic. They clog computer networks. They make computers run more slowly by tying up a computer's processor. They destroy important files. Always be on the alert for viruses, and make sure that antivirus software is installed on your computer.