LockBit Ransomware Abuses Legitimate Windows Defender Utility

The initial target compromise happened via the Log4j vulnerability against an unpatched VMWare Horizon Server. The attackers modified the Blast Secure Gateway component of the application installing a web shell using PowerShell code found documented here. Once initial access had been achieved, the threat actors performed a series of enumeration commands and attempted to run multiple post-exploitation tools, including Meterpreter, PowerShell Empire and a new way to side-load Cobalt Strike. In particular, when attempting to execute Cobalt Strike, Sentinel One observed a new legitimate tool used for side-loading a malicious DLL, that decrypts the payload. Previously observed techniques to evade defenses by removing EDR/EPP’s userland hooks, Event Tracing for Windows and Antimalware Scan Interface were also observed.