Best Free PC Antivirus Software

For Windows PC users, a good antivirus program is a necessity to ward off malware attacks, keep your computer running efficiently, and safeguard your online identity and personal information. Premium antivirus suites have additional features to protect you from malicious Web pages, help you manage security on mobile devices, and monitor your computer's firewall, software updates and other features. But some just don't want to — or can't — pay a yearly subscription fee for those extra features.

If that's you, you've come to the right place. We've evaluated the most widely used free antivirus programs based on ease of use, features, protection and overall system impact.

So which free PC antivirus product is right for you? We reviewed Avira Free Antivirus, Malwarebytes Anti-Malware Free, Avast Free Antivirus, AVG Antivirus Free and Microsoft Windows Defender. Each was tested on the same Windows 8 Acer Aspire E1 laptop, which featured a Core i3 processor and 4 GB of RAM.

Our malware-detection data comes primarily from independent German evaluation lab AV-TEST, which regularly tests all major security software for the ability to detect zero-day malware and other threats.

We also conducted our own tests on how each security suite affected a laptop's performance, running the PCMark7 benchmark software and our own OpenOffice productivity test to assess the system's baseline. We ran the tests again while each security product did a quick malware scan, and then again during full system scans, and compared the results.

Ease of use is also important, which is why we assessed each program on its user interface, and also on how insistently it nags you to upgrade from the free version to a paid edition from the same company.