Tom Deligiannis is an expert in computer security and serves small business. He currently administers multiple networks and shares his knowledge of free or close to free tools that can help protect your business computers.
Check out his blog post titled, “Securing your network and computers on a shoe string budget.“
I, personally, use many of these tools. I’m not a big fan of “free stuff” b/c it’s usually with strings attached, but I can attest to these products. I’ve been computer and virus free for over 3 years.