Windows users began flooding Microsoft support forums last week, saying that their computers had been rendered unusable with a "blue screen of death" (BSOD) error after installing the latest round of security updates from Redmond. The company was forced to stop shipping the MS10-015 update, which was apparently linked to the issue, and said it would investigate further.

Preliminary findings revealed by Microsoft suggested malicious software may be to blame. Today the company was able to confirm this and shared a few more details through a blog post from Mike Reavey, director of the Microsoft Security Response Center. According to Reavey, the blue screen was a result of malware already installed on users' XP machines, specifically the Alureon rootkit, which makes modifications to Windows Kernel binaries and as a result leaves systems in an unstable state.

Microsoft stressed that there were no quality issues with its security update MS10-015, but didn't mention when it will resume distributing it via its Windows Update mechanism. For now the company is working on a simple solution to detect and remove Alureon from affected systems, which it hopes to release "in a few weeks."