Other Threats

Viruses and worms get a lot of publicity, but they aren't the only threats to your computer's health. Malware is just another name for software that has an evil intent. Here are some common types of malware and what they might do to your infected computer:

• Adware puts ads up on your screen.
• Spyware collects personal information about you, like your passwords or other information you type into your computer.
• Hijackers turn your machine into a zombie computer.
• Dialers force your computer to make phone calls. For example, one might call toll 900-numbers and run up your phone bill, while boosting revenue for the owners of the 900-numbers.

As virus creators became more sophisticated, they learned new tricks. One important trick was the ability to load viruses into memory so they could keep running in the background as long as the computer remained on. This gave viruses a much more effective way to replicate themselves. Another trick was the ability to infect the boot sector on floppy disks and hard disks. The boot sector is a small program that is the first part of the operating system that the computer loads. It contains a tiny program that tells the computer how to load the rest of the operating system. By putting its code in the boot sector, a virus can guarantee it is executed. It can load itself into memory immediately and run whenever the computer is on. Boot sector viruses can infect the boot sector of any floppy disk inserted in the machine, and on college campuses, where lots of people share machines, they could spread like wildfire.

In general, neither executable nor boot sector viruses are very threatening any longer. The first reason for the decline has been the huge size of today's programs. Nearly every program you buy today comes on a compact disc. Compact discs (CDs) cannot be modified, and that makes viral infection of a CD unlikely, unless the manufacturer permits a virus to be burned onto the CD during production. The programs are so big that the only easy way to move them around is to buy the CD. People certainly can't carry applications around on floppy disks like they did in the 1980s, when floppies full of programs were traded like baseball cards. Boot sector viruses have also declined because operating systems now protect the boot sector.

Infection from boot sector viruses and executable viruses is still possible. Even so, it is a lot harder, and these viruses don't spread nearly as quickly as they once did. The environment of floppy disks, small programs and weak operating systems made these viruses possible in the 1980s, but that environmental niche has been largely eliminated by huge executables, unchangeable CDs and better operating system safeguards.