Security researcher Abdelhamid Naceri, also known as Nightmare Eclipse, released BigDiskBuster, a Microsoft Defender zero-day that can block antivirus signature and platform updates on supported Windows versions. The disclosure is part of Naceri’s ongoing series of Windows and Defender exploits, following earlier tools like UnDefend and ShieldCrash, with several flaws still unpatched by Microsoft. #BigDiskBuster #UnDefend #ShieldCrash #NightmareEclipse #MicrosoftDefender
Keypoints
- BigDiskBuster blocks Microsoft Defender updates while running in the background.
- Naceri says the exploit works on all supported Windows versions.
- The tool is similar to the earlier UnDefend proof of concept.
- Naceri has released nearly a dozen zero-days since April 2026.
- Microsoft has patched some flaws, but others remain unpatched.