RansomHub Deploys EDRKillShifter Malware to Disable Endpoint Detection Using BYOVD Attacks

 

Sophos security researchers have identified a new malware, dubbed EDRKillShifter, used by the RansomHub ransomware group to disable Endpoint Detection and Response (EDR) systems in attacks leveraging Bring Your Own Vulnerable Driver (BYOVD) techniques. This method involves deploying a legitimate but vulnerable driver on a target device to gain escalated privileges, disable security measures, and take control of the system. 

The technique has gained popularity among various threat actors, including both financially motivated ransomware groups and state-sponsored hackers. The EDRKillShifter malware was discovered during an investigation of a ransomware incident in May 2024. The attackers tried to use this tool to disable Sophos protection on a targeted computer but were unsuccessful due to the endpoint agent’s CryptoGuard feature, which prevented the ransomware executable from running. Sophos’ investigation revealed two different malware samples, both exploiting vulnerable drivers with proof-of-concept code available on GitHub. These drivers include RentDrv2 and ThreatFireMonitor, the latter being part of an obsolete system-monitoring package. 

The malware’s loader execution process follows a three-step procedure. Initially, the attacker launches the EDRKillShifter binary with a password string to decrypt and execute an embedded resource named BIN in memory. This code then unpacks and executes the final payload, which installs and exploits a vulnerable driver to elevate privileges and disable active EDR processes. Once the driver is loaded, the malware creates a service and enters an endless loop that continuously monitors and terminates processes matching names on a hardcoded target list. Interestingly, the EDRKillShifter variants discovered were compiled on computers with Russian localization, and they exploit legitimate but vulnerable drivers, using modified proof-of-concept exploits found on GitHub. 

Sophos suspects that the attackers adapted portions of these proofs-of-concept and ported the code to the Go programming language. To mitigate such threats, Sophos advises enabling tamper protection in endpoint security products, separating user and admin privileges to prevent the loading of vulnerable drivers, and keeping systems updated. Notably, Microsoft continually de-certifies signed drivers known to have been misused in previous attacks. Last year, Sophos identified another EDR-disabling malware, AuKill, which similarly exploited a vulnerable Process Explorer driver in Medusa Locker and LockBit ransomware attacks.