Melissa, I Love You, KAK, Nimda, Red Worm. At some point in the past few years most users on the Internet have encountered at least one of these and more than likely it hasn't been a pleasant encounter. Each one was created to infect your computer with a computer virus.

What is a computer virus? There are actually three different types of programs (I am using this term very loosely) that are generally referred to as viruses. Viruses themselves carry out a specific task and infect programs on your computer. Worms cause problems but do not infect programs. Trojan Horses are hidden inside your computer and may appear useful or funny, but are not. The kind of virus doesn't matter; the damage it can inflict is critical.

What can viruses do to your computer? The most benign viruses may simply post a message on your computer or display something on your screen. The Stoned virus, for example, displayed "Your computer is Stoned" but did no damage. From there, viruses get more insidious. Some, like Melissa and I Love You, send a copy of the virus to everyone in your e-mail address book. Others change the names and extensions of your files making them difficult, if not impossible, to find. Still others garble your files or do something equally devastating.

How can you get a virus? The most common way these days to acquire a virus is through e-mail. Viruses will most likely come as attachments to an e-mail message. Some are identifiable by their extension (the letters after the period at the end of a file name). Common extensions to watch out for are .vbs, .exe, .bat, .mm and files with double extensions (e.g., .jpg.exe). In almost all cases, YOU MUST OPEN THE ATTACHMENT TO ACTIVATE THE VIRUS. Other viruses can enter your computer through floppy disks, downloaded software and even some shrink-wrapped new programs. Additionally, you can get a virus by opening an e-mail in HTML format (this is the language that creates the layout for web pages). An HTML e-mail will look like a web page.

How do you know if you have a virus? The most common symptoms of a virus include:

• Programs take longer to load.
• Program sizes keep changing.
• The hard drive light flashes when you are not doing anything.
• Files have strange names that you don't recognize.
• Unknown files show up on your computer.

How can you practice "safe computing?"

1. Do not open an attachment unless you are expecting it. If an attachment comes unexpectedly, and you don't know the sender, delete it. If you know the sender, e-mail or phone and ask if he/she intended to send the attachment to you and why they sent it and what it is.
2. Do not use pirated (copied) software.
3. Install a virus protection program on your computer and set it to scan incoming attachments and e-mail messages. The best sellers are Norton AntiVirus (http://www.symantec.com/) and McAfee VirusScan (http://www.mcafee.com/).
4. Update your virus program regularly. Each of these programs creates updates as new viruses arrive on the scene. With the click of a button you can visit their website and obtain the latest virus definitions.
5. Use the anti-virus program to scan your computer regularly.
6. Back up your computer files on a regular basis (most experts recommend weekly backups). Purchase an external hard drive. If your computer has a USB port (now on most new and recently purchased computers) you can buy a large one (25-30 gigabytes) for under $200.
7. Tell Windows to display all file extensions. To do this you can double click My Computer on your desktop. Next, pull down the view menu and click Folder Options. If there is nothing listing Folder Options, click Tools. Next, click on the tab labeled View. Change the setting under Hidden Files to view all files by checking that box. Now uncheck the box labeled Hide File Extensions for Known Types of Viruses. Click OK.
8. Turn off Windows Scripting Host (a common way to create viruses). Click the Start button (lower left corner), click Settings and then click Control Panel. Double click Add/Remove Programs and click on the Windows Setup Tab. Double click Accessories and the uncheck Windows Scripting Host (near the bottom of the list).
9. If you use Internet Explorer, Microsoft Outlook or Outlook Express, update them by visiting windowssupport.Microsoft.com and downloading the latest patches and updates. If you use Eudora (http://www.eudora.com/) or Netscape Messenger (home.netscape.com/smartupdate) visit their websites for recent updates. If you use a Mac, you can (almost) breathe a sigh of relief since nearly all viruses are written for PCs (who own 90% of the market).
10. Visit http://www.getvirushelp.com/ for valuable information and updates about current viruses.

Take the 10 precautions listed above and you will probably never contract a computer virus. One note: There are lots of viruses out there, but there are also lots of "virus hoaxes." Visit http://www.vmyths.com/ for excellent information on this topic.

Copyright, 2002, The National Psychologist. Reprinted with permission. The National Psychologist is a privately-owned bimonthly newspaper which may be purchased for $30 a year. Write or call: TNP, 6100 Channingway Blvd., Suite 303, Columbus, OH 43232; telephone: 614.861.1999 or fax with Visa or MC to 614.861.1996.