BTR Reforged: Weaponizing Defender’s Remediation Driver as a Kernel Operation Primitive

Research by: Jiří Vinopal ( @vinopaljiri ) Abstract What if a trusted security component could be repurposed into an attacker-controlled kernel primitive? What if a signed Microsoft remediation driver could be instructed to execute arbitrary file and registry operations from Ring 0 – without exploits, vulnerabilities, or memory corruption? In this publication, we present the first full reverse engineering of the Windows Defender Boot-Time Removal driver ( BTR.sys ) and its proprietary transactio