The government agency took two PCs running a fully-patched Windows 7 with the Microsoft Security Essentials (MSE) antivirus package installed.

FORBES: Six Simple Steps Proven To Keep Your Windows 7 PC Safe From Hackers And Malware

The free Microsoft Security Essentials tool is ideal.

FORBES: Six Simple Steps Proven To Keep Your Windows 7 PC Safe From Hackers And Malware

The statistics in the report were gathered from the 600 million machines that are enrolled in Microsoft's various update services or use its Essentials and Defender security packages.

BBC: Two million US PCs recruited to botnets