Researchers in the anti-virus and anti-spyware world are losing the battle against "botnets," the millions of zombie PCs that are used to send out spam and other nasties.

Simply put, a botnet is a collection of PCs with high-speed connections that have been hijacked.

Estimates are there are millions of compromised PCs (many in homes) that are waiting to be used by gangs that are used mostly to send trillions of spam messages all over the world.

Symantec, the anti-virus vendor, did a study that found 4.7 million infected computers during one scan it performed. And that surely didn't get them all.

If you've been getting those penny stock pitches in your e-mail (or notes offering sexual aids, herbal medicines or illegal software) you've been the victim of a spam attack from a bot. And the problem is only increasing.

What can you do to prevent a bot from taking over your system?

The most important thing is to install all critical Windows patches from Microsoft. In my repair business, I would imagine 75 percent of the machines that come to our shop with issues are unpatched. Granted, Microsoft doesn't make it all that easy (especially for dial-up users), but you need to make sure you're protected. (Once you get patched all the way you can turn on "Automatic Updates," which will download and install the latest patches for you automatically.)

So to get patched, launch Internet Explorer and go to update.microsoft.com. Run the scan and install all of the critical and high-priority updates. It may take several reboots and visits to the site to get all of the patches done. But take your time and do them all.

Then turn on Automatic Updates (on the right side of the page), and that will keep your computer up to date.

(The patches download in the background when your computer is idle.)

Secondly, make sure you have a firewall installed. If you're running Windows XP and are not incredibly computer savvy, the Windows firewall is good enough.

After you have run all of the patches, go to START then the CONTROL PANEL and pick Windows Firewall. Make sure it is turned on.

If you want to use a third-party firewall, you can get a free version of the excellent Comodo firewall at www.comodo.com. A firewall also is built in to Norton Internet Security and some other security suites.

Lastly, make sure you have a current anti-virus product installed. For home use I recommend the excellent AVG Free Edition 7.5, which you can get at www.filehippo.com or the Comodo Free Anti-Virus at www.comodo.com. These free products do a good job, and you can save significantly on license and renewal fees.