Sadly, computers were a lot safer before people figured out how to link them into the giant network called the Internet. Although viruses dominate today's technology news, they first appeared on PCs in 1986. Back then, just about the only way a virus could travel from one desktop computer to another was on an infected floppy disk. So although viruses have been around for a couple of decades, it took the Internet to make them truly dangerous.
Nowadays, malicious programs can email themselves to everyone in your Windows computer's address book before you know it. They can secretly transmit information about your shopping and surfing habits back to unseen companies and pepper your screen with advertisements. A particularly virulent outbreak of nasty programming code can even crash Windows computers and grind the Internet to a halt.
Viruses, worms, and their ilk usually hitch rides on email messages sent from infected computers (whose owners probably have no idea they're infected). Or perhaps yet another angry, frustrated programmer launches a mass mailing of malicious code in a desperate cry for attention.
Fortunately, plenty of antivirus programs can swat down pestware before it has a chance to infest your PC. A good antivirus program also screens your mail for you. (A decent junk mail or spam filter on your email program can isolate messages emailed to a ton of people. See Section 14.4.3 for more on how to activate the built-in spam filters you may already ...