(FORTUNE Magazine) – We are entering the plague years for computer viruses. There are more viruses appearing than ever before, and unlike earlier versions, which were mainly annoying, these new ones are increasingly more destructive. They spread faster too. An increasingly common category of viruses called worms spread from computer to computer over networks like the Internet. If you download files from the Internet and swap e-mail with other people, sooner or later someone will send you a virus.

The good news is that it's relatively easy to avoid becoming infected. All it takes is common sense, a good antivirus program, and good antivirus habits. Here are the basics:

Step 1: Back up your hard disk drive.

Step 2: Repeat Step 1 regularly. This way you'll minimize the damage in case you do get hit by a virus.

Step 3: Buy an antivirus program. There are several good ones, but the one I recommend is Norton Antivirus, which comes in versions for Windows PCs ($39.95) and Macintoshes ($69.95), or, even better, as part of the Norton Internet Security package ($69.95 Windows, $99.95 Mac). Before you spend money on a program, though, check to see if an antivirus utility has already been installed on your PC at the factory. Also, Norton (www.symantec.com) and several other antivirus programs are available online for free trials.

Step 4: Update the virus program regularly over the Internet to make sure it can detect the virus du jour. The Internet has accelerated the speed at which new viruses spread; if you don't update your virus signatures regularly--say, once a week--you reduce the effectiveness of your antivirus software. I like Norton Antivirus because it updates itself automatically every time I connect to the Internet.

If you think you've been nailed by a virus already, skip the first two steps and go immediately to Nos. 3 and 4. Otherwise you risk backing up the virus along with your data.

Step 5: Never open an e-mail attachment unless you're positive it does not contain a virus. Worm viruses often propagate by hijacking the victim's e-mail address book and sending themselves to everyone in it. Consequently the virus often arrives attached to a message from a friend, saying something like, "Hey, check out this picture of Jennifer Lopez naked!"

Step 6: Don't fall for virus warning hoaxes, which are even more common than viruses. You've probably received an e-mail message from a well-meaning friend, warning you about some terrible new virus that will melt your hard disk, curdle the milk in your refrigerator, and make your toenails fall out. Don't pass along the warning to everyone you know; instead, visit the virus and e-mail hoax-buster site at http://hoaxbusters.ciac.org.