Seth Rosenblatt/CNET

Microsoft defended what it called the "exceptional" step of a "limited review" of a blogger's Hotmail account as part of a larger Windows espionage case, saying it had caught the blogger selling Microsoft's intellectual property without permission.

A court filing alleges that the unnamed blogger had been provided prerelease Windows 8 RT source code by then-Microsoft employee Alex Kibkalo. Kibkalo is being charged with stealing trade secrets.

The filing says that Microsoft triggered an internal investigation into the blogger's actions when the blogger sent the source code to an unnamed person, hoping for verification of its origins. Instead, that person tipped off then-Windows chief Steven Sinofsky, who forwarded the details to Microsoft's Trustworthy Computing Investigations department, which investigates external threats and internal information leaks.

The March 17 filing (PDF) alleges that the unnamed blogger confessed to selling Microsoft's intellectual property.

During his interview, the blogger admitted to posting information on Twitter and his Web sites, knowingly obtaining confidential and proprietary Microsoft IP from Kibkalo, and selling Windows Server activation keys on eBay.

Microsoft provided CNET with a statement defending its actions: