What is going on with my computer? One day it works and the next day I cannot use any software program.

Chances are your computer has been infected with a virus, Trojan horse, or worm. These are computer programs or pieces of computer code that have been delivered to your computer either through the Internet, a floppy disk, or a CD-ROM/DVD. It is much like contracting a contagious disease. You have to be in the wrong place at the right time!

What is a virus?—A computer virus is a small program written to alter the way a computer operates, without the consent of the user. In order for a virus to interrupt the way a computer works, it must associate itself with a commonly used program on the computer that will allow the virus to start its damage. Once started, the virus must "replicate" or copy itself and will often replace properly working program commands.

Viruses can be as simple as flashing a strange message on your computer to completely destroying the computer's storage cabinet known as the hard drive. Some virus will also use up the computer's resources and will often cause erratic behavior and the computer will stop responding, also known as a "system crash."

What is a Trojan horse?—No, we are not in Troy and there are no Greek soldiers hidden in a large wooden horse. However, the name, Trojan horse, is appropriate for this computer fraud. This type of infection typically attaches itself to an email containing content that would peak your interest such as a picture or a great joke. By opening the email attachment, you "invite" the Trojan horse into your computer much like the citizens of Troy with the wooden horse. Once triggered, the Trojan horse can cause loss or even theft of information on your computer. The main difference from a Virus is that a Trojan horse does not need to "replicate" itself. It has done its deed. One example of a Trojan horse is called PWSteal.Trojan.D. PWSteal will attempt to steal your login names and passwords. These passwords are sent to the author of this Trojan horse through an anonymous email address.

What is a worm?—Worms are programs that can replicate themselves from one computer system to another. A worm will wind its way from one computer to another cleverly concealed inside other files like Word or Excel documents, also know has "host files." The host document will email itself to other computers by using the Internet address book it finds on each machine. One example of an email worm is W32.Magistr.24876. This worm arrives as an attachment to an email. The worm has appended part or all of a random document taken from the infected computer to itself and then sends this new file via the sender's email address book. This is how the worm propagates itself. This worm causes system instability and can send confidential Microsoft® Word documents to others.

Where Do Viruses Come From?—I'm often asked this questions and my standard answer is, "They are created by people who have too much time on their hands!" Viruses are developed for a variety of reasons that ranges from "because it was there" to those who want to steal your identity through your computer.

Keeping Your Computer Healthy—In 1987 a virus was found on ARPANET (Advanced Research Projects Agency + NET), which was a large network used by the Defense Department and many universities and the forerunner to the Internet. A new business was born-electronic security. A software program commonly called an anti-virus program was developed that would periodically check your computer systems for known viruses. Once properly installed on the computer, the anti-virus software helps to protect against a large array of viruses. To maintain this level of protection, each new virus must be identified and a recommended "fix" is offered to the user. Since new viruses are created almost daily, the computer user must continually update their virus definitions. This is done through an Internet connection to the software developer. Two well-known commercial developers of security software are Symantec's Norton AntiVirus and McAfee VirusScan. ©2002 The Computer Teacher, All Rights Reserved