Researcher Naceri releases 'BigDiskBuster' zero-day blocking Windows Defender updates

Security researcher Abdelhamid Naceri published a new proof-of-concept exploit called BigDiskBuster that, when run in the background, prevents Microsoft Defender from installing platform or signature updates on any supported Windows version. Naceri describes it as similar to his earlier UnDefend exploit, and says the code is still buggy but demonstrates the concept clearly. This is the latest in a string of nearly a dozen Defender and Windows-related exploits he has released since April 2026 amid an ongoing dispute with Microsoft over his termination.