Avast Free Antivirus is one of the best free antivirus programs you can download. I've used it on and off over the years and generally liked it, except for a few drawbacks, which are discussed below.

This is a complete tool that protects against threats from the Internet, email, local files, peer-to-peer connections, instant messages and much more. It even outperforms its competitors by quite a bit.

With all these features, you might be wondering what you're paying for it. Luckily, as the name suggests, it's completely free for Windows and Mac!

Avast's free AV program includes fully functional antivirus, antispyware, and heuristic engines. There's also real-time protection for files, email, web browsing, and suspicious behavior. It also scans browser plugins to find installations that have a bad reputation and are potentially harmful.