Lifehacker reported in December that Microsoft’s new antivirus and antimalware utility Microsoft Security Essentials ranks as the best performing free antivirus tool:
AV-Comparatives.org ran a series of real-world tests running through common scenarios like downloading, extracting, copying, and encoding files, installing and launching applications…Not only is [Microsoft Security Essentials] one of only three products that both blocks and removes malware well, but it’s also very light on system resources.
You can download Microsoft Security Essentials for free from the Microsoft site. If you or your company already has a paid subscription to an antivirus utility, there is no need to download another one. However, if you are thinking of switching from a different free utility or need an antivirus utility for your home PC, Microsoft Security Essentials is a tried and highly recommended security solution.