CSAgent.sys

ABYSSWORKER is a malicious driver used in MEDUSA ransomware attacks to disable EDR systems. The driver masquerades as a legitimate CrowdStrike Falcon driver and provides extensive capabilities to terminate processes, remove security callbacks, manipulate files, and disable security tools. It uses stolen certificates from Chinese companies and requires a specific password for activation. The driver was observed being deployed alongside HEARTCRYPT-packed loaders and provides attackers with kernel-level capabilities to blind EDR products by removing notification callbacks, detaching mini-filter devices, and replacing driver major functions.

sc.exe create CSAgent.sys binPath=C:\windows\temp\CSAgent.sys type=kernel && sc.exe start CSAgent.sys