Microsoft Defender's Own Driver Weaponized for Endpoint Security Bypass
In August 2026, Check Point Research disclosed a technique that weaponizes Microsoft Defender's own legitimately signed boot-time remediation driver (BTR.sys) to perform arbitrary kernel-level file and registry operations on Windows systems. The technique, dubbed 'BTR Reforged,' affects all Windows versions from Windows 7 through Windows 11 25H2 and exploits a built-in driver that cannot be blocked without disrupting Defender itself. Researchers demonstrated live deletion of the entire Defender stack on a fully updated Windows 11 system with Tamper Protection active, requiring only administrator privileges with SeLoadDriverPrivilege. Unlike traditional bring-your-own-vulnerable-driver attacks, this technique uses infrastructure present in every Windows installation, making it particularly concerning for endpoint security bypass scenarios. This discovery highlights the evolving sophistication of endpoint security bypass techniques, where attackers increasingly leverage legitimate system components rather than external vulnerable drivers that can be easily blocklisted by security vendors.
Kill Chain
