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Viruses

Trust no one

Computer viruses are mysterious and grab our attention. Days past you didn’t have worry about email viruses if you only opened attachments sent from someone you knew. Those days are gone.

For example, the thing making big news right now is the Mydoom worm, which expert’s estimate infected approximately a quarter-million computers in a single day. Once the virus has built itself an email address list, it sends itself to those addresses without the unsuspecting victim even knowing it is happening.

It is more likely you will receive an email virus from someone you know, rather than someone you don’t know.

What's a "Virus"?

Computer viruses are called viruses because they share some of the traits of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person.

There are similarities at a deeper level, as well. A biological virus is not a living thing. A virus is a fragment of DNA inside a protective jacket. Unlike a cell, a virus has no way to do anything or to reproduce by itself -- it is not alive. Instead, a biological virus must inject its DNA into a cell. The viral DNA then uses the cell's existing machinery to reproduce itself. In some cases, the cell fills with new viral particles until it bursts, releasing the virus. In other cases, the new virus particles bud off the cell one at a time, and the cell remains alive.

A computer virus shares some of these traits. A computer virus must piggyback on top of some other program or document in order to get executed. Once it is running, it is then able to infect other programs or documents. Obviously, the analogy between computer and biological viruses stretches things a bit, but there are enough similarities that the name sticks.

Type of Infection

When you listen to the news, you hear about many different forms of electronic infection. The most common are:

  • Viruses - A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc.
  • E-mail viruses - An e-mail virus moves around in e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book.
  • Worms - A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well.
  • Trojan horses - A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically.

Watch attachments

Look for these extensions on file attachments: .exe, .vbs, .bat, .pif, .scr, and .com. Any files with one of these extensions is an executable file. If you are unsure about the attachment do not open it, delete the message. You can scan for viruses before opening it.

You should make sure that Windows is not configured to hide known extensions. Instructions for updating your settings follow:

For Windows 95, 98 and Windows NT 4.0:

  1. Click the Windows Start menu.
  2. Select Settings, Control Panel to open the control panel.
  3. From the View menu, select Options.
  4. Click the View tab.
  5. Uncheck Hide files of these types and Hide file extensions for known file types.
  6. Select Show all files.
  7. Click OK.

For Windows 2000:

  1. Click the Windows Start menu.
  2. Select Settings, Control Panel to open the control panel.
  3. From the Tools menu, select Folder options.
  4. Click the View tab.
  5. Select Show hidden files and folders, which is under Hidden files and folders.
  6. Uncheck Hide file extensions for known file types.
  7. Uncheck Hide protected operating system files.
  8. Click Yes to confirm.
  9. Click OK.

Protect yourself

The best line of defense is to have up-to-date virus protection software. There are many products available, make sure you get regular updates. Most programs allow you to automatically download updated virus definitions. Back up your data regularly so you can restore valuable files in case of a virus attack.

For a list of anti-virus vendors, check out www.cert.org.

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