I personally run the paid version of Kerio Personal Firewall and the free version of AVG (Anti-virus). I them set to auto update and run them daily at like 5am. Those constantly run in the background. *Kerio does offer a free version of their firewall.
*If you run a router, many contain firewalls - just make sure yours is configured properly.
I also have Ad-Aware (freeware), and Spy Sweeper for all those little, nasty, spyware programs that try and sneak onto your system. They can slow you down to a smails pace! All of a sudden that nice new PC runs like a cripple - you know. lol *One more freeware program is Spybot - just note this is not for the casual user, you can delete some important files using that, so be cautious.
Ewido Security Suite is the last thing I keep on hand. It is wonderful and designed for:
Hijackers and Spyware
Worms
Dialers
Trojans and Keyloggers
*Ewido will allow you to run a free scan here, you may be very surprised at what you find living on your system!
Ewido and the spyware programs I run on an intermittant basis, or if I notice a change in performance.
When it comes to spyware, it is a good idea to have more than one tool on hand in case the first program does not get your "bugs". No single program can find and eradicate all spyware.
There are a number of groups who will rate these programs for you - cnet being one of the better known. But read about them and pick the one that works for you and the one that you feel comfortable with...
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All these things are very important esp if you go to some of the more notorius sites.
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One more thing, your choice of web browsers will influence the number of spyware programs and vulnerabilities you are exposed to....
Internet Explorer is one of the riskiest to use - because they are the biggest target and peeps find their biggest pool of victims there. Also, since it comes on most PCs - the less tech savvy will automatically use it...
Firefox is butter, but does seem to be getting more attention lately from people wanting to cause problems.
Opera (just recently free) is probably your safest bet today. You have a good concentration of knowledgeable people working together to make it one of the best out there. I have been using Opera for the past 2 years, but do have all three on my system for specific applications.