How can my computer be infected with a virus?

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. These infected files are typically found in newsgroups or on sites that are not officially authorized to distribute the software, such as peer-to-peer networks. Computer viruses can also be sent through e-mail. As a safety 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 some other convencing subject, 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 virus 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 detection is that the scanner must recognize the fingerprint in order to identify the file as infected. For this reason, it is imperative that you keep the signature update files up-to-date by checking for periodic updates on the product manufacturer's Web site.

To detect unknown viruses, combinations of techniques are used, some call it "Heuristic" scan. One of them is the "Checksum comparison" and "intelligent checksum analysis" which help 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" also known as "Real Time Monitoring" (RTM) or "Real Time Scanning" is a technique that runs in the background and continuously scans all files as they are used, meaning, opening, closing, or saving a file. This allows the RTM monitoring to protect your system continuously and without user intervention. RTM 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:

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