Worms, viruses and Trojan horses? No, we�re not talking about those outdoor squiggly creatures, the causative agent of an infectious disease, or the deceptive wooden horse in the Greek legend. Rather, these terms refer to the varying strains of digitally degenerative parasites, or destructive viral programs.

According to NetLingo, a virus is a program that replicates itself on computer systems by incorporating itself into other programs that are shared on a system or network. They�re known for their ability to spread overnight from one computer to millions of others around the world, causing them to crash.

A computer worm is a self-contained program (or set of programs) that is able to spread functional copies of itself or its segments to other computer systems. The propagation usually takes place via network connections or email attachments. To get rid of a worm you just need to delete the program.

As its name implies, a Trojan horse is a type of computer virus that comes disguised as a program that performs some unexpected or unauthorized, usually malicious, action, such as displaying messages, erasing files or formatting a disk. A Trojan horse doesn�t infect other host files, thus cleaning is not

necessary. It usually happens like this: People download a program from the Internet, start it up, and then find out it contained a virus after it erases their hard drive and wreaks havoc on the computer system.

Compared to five years ago, viruses are now more destructive, and less prone to early detection by the average computer user. Years ago, computer viruses were taciturn, frustrating, and only sometimes devastating, typically transferred from computer to computer (similar to the spread of poison ivy) through shared disks. Today�s viruses are so clever they can deceptively address you by name and send you information you supposedly requested. They can even deceive you into thinking you�ve received a message from your bank, your credit card company, or someone you supposedly know. Viruses surreptitiously propagate with deadly swiftness; they can use macro languages to perform automated tasks and automatically email themselves to everyone in your address book shortly after infecting your computer. All it takes is executing the wrong attached file from electronic mail and you can trigger the launch of a nasty virus program within your system. Then, your computer can experience symptoms ranging from a few malfunctioning programs and deleted files to the complete expunging of your hard drive and crashing of your computer.

 How viruses work

In a nutshell, here�s how viruses work: A virus contains precisely programmed instructions to self-replicate over and over again. After gaining initial entry to your system � through an infected email attachment, or a program downloaded from the Internet � the virus attaches itself to your computer like a leech. From there, it infects any program that you attempt to open and run. Viruses can rewrite your computer program in seconds, instructing it to allow the virus to run first. Then, it�s only a matter of time before the user realizes that the computer has been attacked by a malicious computer virus.

Seeing as the �bad guys� seem to be getting smarter (and younger), computer users should get smarter, too. Educate yourself on the various virus strains that are currently �in the wild,� as they say. Install anti-virus software on every computer and network server. Back-up your computer�s content regularly with a reliable backup program. Virus definitions should be updated monthly, too, and any questionable files received via email should be saved to a disk and scanned before opening. 

Before purchasing any anti-virus software, check out thorough reviews at http://anti-virus-software-review.toptenreviews.com.

McAfee.com suggests computer users take the following precautions in order to avoid computer viruses: Don�t open any files attached to an email from an unknown, suspicious or untrustworthy source. Don�t open a file attachment unless you know what it is, even if it appears to come from someone you know. Delete junk email and don�t forward or reply to them. Exercise caution when downloading files from the Internet by ensuring the legitimacy of the source. Update your anti-virus software regularly because over 500 viruses are discovered each month. Back up your files on a regular basis. If a virus destroys your files, at least you can replace them with your back-up copy. When in doubt, always err on the side of caution and do not open, download, or execute any files or email attachments. Not executing is the most important of these caveats.

It is said that 1 in every 30 computers will be infected by a virus this year. Take the necessary precautions to make sure that yours isn�t that one.

For information on other types of viruses not mentioned in this article, visit www.buzzle. com/articles/different-types-of-computer-viruses.html.