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."