Your system can become infected with a computer virus in several different ways. One of the most common methods is by downloading infected software from the Internet. Most infected files are found in newsgroups or on sites that are not officially authorized to distribute the software. Computer viruses can also be sent through e-mail. As a precaution, never open e-mail attachments from people you don't know. Many times, however, the infected e-mail will appear to be from a friend or coworker, usually with a file attached and a message saying, "Hey, check this out!" or "Here's that file you wanted!" and it contains a virus.

Fortunately, there are tools available that are able to detect and eliminate computer viruses. Anti-virus tools use several different techniques to detect and remove computer viruses, and they are one of the easiest and most effective ways to protect your computer against unwanted attacks and malicious destruction of data. "Signature-based analysis" is the most common and most effective technique. Signature-based scanners examine every file on the drive looking for a virus fingerprint. A fingerprint is a string of code that is unique to a specific virus. Signature-based scanners use this fingerprint to identify infected files by comparing it to a catalog of all known virus fingerprints. A limitation of signature-based analysis is that the scanner must recognize the fingerprint in order to identify the file as infected. For this reason, it is important to keep the signature catalog current by checking for periodic updates on the product manufacturer's Web site.

To detect unknown viruses, combinations of techniques are used. "Checksum
comparison" and "intelligent checksum analysis" accomplish this task by comparing the current fingerprint of a suspect file, called a checksum, to the checksum recorded when the file was known to be clean. Changes in the checksum can alert the program to file changes caused by a virus. "Expert-system virus analysis" can detect unknown viruses without having any previous file information to use for comparison. It can also analyze unopened files to protect against re-infecting your system.

"Terminate-and-stay-resident (TSR) monitoring" is a technique that runs in
the background and continuously scans all files as they are used. This allows
TSR monitoring to protect your system continuously and without user intervention. TSR monitoring can use any combination of protective techniques.

The best anti-virus program is one that uses all these techniques to provide comprehensive protection against computer viruses.

More information about virus protection software can be found by visiting the
following manufacturer or provider websites:

• McAfee


• Vcatch


• Norton AntiVirus