David is trying to find an antivirus for Windows 7. Leo says that Microsoft's own Security Essentials (or Defender, depending on the version) is sufficient, and it's free. The problem is that viruses are usually coming out so fast (called zero day exploits) that you can get infected before the AntiVirus finds it and removes it. Then the viruses are often attached to a system file and it renders the computer unusable. Even security experts put antivirus low on the list of things to do to prevent infection.
The ultimate protection is your online behavior. Here are some steps to protect yourself from viruses and malware:
1. Operate as a limited user instead. Add an account as an administrator and then demote your existing account to limited user. This will stop over 90% of all the exploits out there.
2. Stop using Internet Explorer. Go with Google Chrome. It's free and far more secure.
3. Don't click on links in email.
4. Only get your software from original vendors.
5. If you use one, keep antivirus software up to date.
6. Stop using Java.
7. Use a password vault like LastPass.
8. Turn on second factor authentication.
Vigilance is your best protection. Ultimately, though, if you're a target for hackers, it'll be almost impossible to protect yourself. In February, Kevin Roose from Fusion dared two expert hackers to hack him. He wound up getting tricked by an email that they sent him, and they were able to take over his computer's camera, microphone, and even his speakers. Read the full article at Fusion.net.