Abdelhamid Naceri releases BigDiskBuster exploit targeting Microsoft Defender

Security researcher Abdelhamid Naceri, known online as Nightmare Eclipse, has released a new proof-of-concept exploit named ‘BigDiskBuster’. The exploit targets Microsoft Defender, functioning as a denial-of-service attack that prevents the antivirus software from completing platform and signature updates. Naceri claims the tool works on all currently supported versions of Windows, though he noted the code remains buggy.

This release follows Naceri’s recent decision to reveal his identity and share details regarding his abrupt termination from Microsoft. He alleged that his dismissal was unjustified and described a difficult legal battle in a German labor court that ultimately upheld the company’s decision. Naceri has published approximately a dozen zero-day exploits targeting Windows since April 2026, including previous tools such as UnDefend and ShieldCrash.