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Computer Viruses

Even people who've never touched a computer have heard ominous tales about computer viruses. A virus is a program, generally designed by a bright but maladjusted computer nerd, that in one way or another interrupts or undermines the normal workings of your computer. Viruses work by copying themselves into legitimate files, called hosts. From there, they often branch out, replicating themselves in more and more files on the disk. Although some viruses infect almost every file in sight, others are pickier: Some viruses only infect application programs, others infect data files, and still others invade the operating system itself.

What Viruses Can Do

The level of destructiveness of viruses varies widely. Some viruses display pictures or messages on the screen periodically. Others erase or destroy programs and data. They also wreak havoc at different speeds: Some viruses spread through your system fairly quickly but don't actually do anything for days or even months. Macro viruses are a relatively new form of virus that currently affect only documents created in Microsoft Word and Excel.

Figure 3.23

How You Get a Virus

Viruses are often passed via disk: You buy or are given a disk that already has the virus on it. Some PC viruses are only passed if you boot (start your computer) from an infected disk—turning your computer on with the disk already in the floppy drive. Others can infect your system when you copy a file from an infected disk or even when you attempt to erase an infected disk. Viruses can also be passed when you use a modem to download (copy) a file from the Internet or access data or programs on a network. Many viruses also arrive in files attached to emails. The chances of contracting a virus are small if you only install commercially available, shrink-wrapped programs and rarely exchange disks with anyone else. The more computers your system comes in contact with—via the Internet or via floppy disks—the greater your risk.

Figure 3.24

Make Regular Backups

There are several steps you can take to protect your system from viruses: For starters, you should back up your data religiously, and don't discard or overwrite all your older backups. (You'll learn more about backups in Chapter 7.) It may take you days or weeks to notice and diagnose a virus, and many of your files may be damaged in the meantime. If you back up your data every day, you may just be backing up damaged files. What you need is an older copy of the data, one made before your computer was infected.

Write-protect Your Floppy Disks

You should also write-protect floppy disks whenever possible. Because viruses cannot infect write-protected (locked) disks, you should write-protect any disks that you don't need to copy files to—in particular, your original copies of unprotected program disks—before you insert them into your computer. That way, if you install the program and the copy that resides on your hard disk becomes infected, you can always reinstall from your write-protected floppy disks.

Use Antivirus Programs

In addition, you should use antivirus programs. The program will check your hard disk for viruses as soon as you turn on your computer, as well as scoping out any floppy disks you use over the course of the day.

Figure 3.25

Viruses Don't Cause All Computer Problems

Now that you know what viruses are, don't start blaming them for everything that goes wrong with your computer. Most problems you encounter on computers will be due to hardware problems, program bugs (mistakes within the program), or typos and other "user errors." If your computer starts displaying odd messages or if you keep encountering little happy faces in your word processing documents, by all means, investigate virus protection programs. But consider some of the other possibilities first.

Antivirus Programs May Conflict with Other Programs

If you install an anti-virus program and then start experiencing problems with other programs, see if uninstalling the antivirus program solves the problem.

Popular Antivirus Programs

The most popular antivirus programs are Norton Anti-Virus (produced by a company named Symantec), and McAfee's VirusScan.

Watch Emails Carefully

Never open or activate any file that is attached to an email unless you have a virus-protection program running. Many viruses are spread through email, sometimes inadvertently by people you know.

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