I hate writing about computer viruses. It always reminds me of how many unscrupulous, money-hungry people there are in the world.

Yet there are times when I feel that I must write about a certain virus because it is causing so much havoc for everyday computer users. Unfortuna-tely, that time has come again.

In the past two weeks, my company has removed a very bad group of viruses from six different computers. So I feel it is time to send out a warning.

There are many different variations of this virus and its cousins. They have many different names, including Antivirus 2008, Antivirus 2009, SpywareScanner 2008 and AntiVirXP08.

Some experts are calling them viruses. Some are calling them malware. Symantec calls them misleading applications. McAfee lists them as PUPs (potentially unwanted programs). Whatever you call them, they are terribly invasive.

By most accounts, these awful applications piggyback on programs that are downloaded from the Internet. However, some experts are warning that your computer may become infected by simply visiting certain Web sites, especially if your operating system and/or antivirus software is not up to date.

The gist of the matter is that once your computer is infected, you will begin to see pop-up windows that give an exaggerated report of the number of threats infecting your computer. The window may say something like, "Your computer has become infected with 231 computer viruses and spyware." These pop-ups try to scare you into purchasing their antivirus or antispyware software.

If you purchase it, they send you a registry key, but it doesn't work because the program they sell you doesn't exist. These viruses are also being spread by malicious Web sites that sell fake antispyware software. On top of that, there are many other viruses or pieces of malware that can piggyback on the main virus. So this malware can dramatically slow down or even stop your computer.

The infections being caused by these viruses and malware programs are extremely harmful and can be very difficult to remove. They often require a cleanup by a professional or a complete reformatting of the hard drive and reinstallation of the software.

As an everyday computer user, you need to be very careful about the software you download from the Internet. Make sure that it is from a source that you know to be reputable or a Web site that has been recommended by a trustworthy source.

You can also use a program such as McAfee Site Advisor to help you assess the validity of the Web site before you download the program. McAfee's Site Advisor is a small program that is used by your Internet browser to indicate the safety of Web sites. It is a free download available at www.siteadvisor.com -- it is a valuable tool.

Also, as usual, be sure that you update your operating system and antivirus software regularly. Don't fall for any program that pops up on your computer trying to scare you into purchasing antivirus or antispyware software.

Yes, the bad guys are out there, and they have a lot of computer savvy. So we all need to be smart about the software we download and the Web sites we visit.

Sandy Berger welcomes all of your quests and comments on today's column. Please post them on the Compu-Kiss Message Board at www.compukiss.com/happycomputing.