Now the free version is very basic, but good enough for most people. You can pay to upgrade for more protection, but I don't think most people really need to. Here's the link!
For even more security you also need a firewall! It keeps the hackers from being able to access your computer from a remote location. Once you have these two products, you'll be a lot safer.
Antivirus software protects you from known viruses and can help clean up after a virus attack. But only a PC firewall can block unauthorized access to your Internet-connected computer and protect against both known and unknown malicious software and Internet threats.
The one I recommend is Zone Alarm Free Version by Zone Labs. I t gives you a very good basic firewall which is all most users should need. Now if you have windows xp, you already have a firewall built in. But here is the link,
Two other programs that can keep your computer clean are Ad-Aware SE,
With the ability to scan your RAM, Registry, hard drives, and external storage devices for known data-mining, advertising, and tracking components, Ad-Aware SE easily can clean your system, allowing you to maintain a higher degree of privacy while you surf the Web.
And Spybot - Search and Destroy!
Spybot - Search & Destroy detects and removes spy ware. Spyware silently tracks your surfing behaviour to create a marketing profile for you that is transmitted without your knowledge to the compilers and sold to advertising companies.
Make sure you run them regularly and update them often and you can surf the net safely!