RansomHub Ransomware Using Multiple Techniques To Disable EDR And Antivirus

The RansomHub ransomware group tracked as Water Bakunawa, employs targeted spear-phishing to exploit the Zerologon vulnerability, allowing them to gain unauthorized access to networks, affecting various industries and critical infrastructure sectors, demanding ransom payments for data release. 

The group’s recent integration of EDRKillShifter, a tool designed to evade detection and disrupt security processes, poses a significant threat to endpoint security, whose ability to dynamically disable EDR solutions and ensure persistence makes it a formidable adversary for traditional security measures.

A ransomware group typically gains initial access to systems by exploiting vulnerabilities, phishing, or password spraying. A compromised user account was the primary entry point in a specific incident, with multiple spear phishing attempts detected. 

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The Zerologon vulnerability was identified as a potential access vector, as the Vision One telemetry dataset revealed detections indicating the abuse of elevation control mechanisms, further suggesting the presence of malicious activity.

RansomHub’s evasion tactics employed four batch scripts to disable security measures and facilitate unauthorized access, as 232.bat used password spraying and disabled Windows Defender. 

Tdsskiller.bat modified the registry, terminated processes, and disabled Trend Micro’s antivirus service, and Killdeff.bat, an obfuscated PowerShell script, manipulated Windows Defender settings and attempted privilege escalation. 

LogDel.bat altered file attributes, modified RDP settings, and cleared Windows Event Logs to hinder forensic analysis, which compromised system security and enabled RansomHub to execute its malicious payload.

The EDRKillShifter tool, a BYOVD loader, uses a password-protected command line to execute and decrypt an embedded resource named “data.bin,” and then unpacks and executes a second-stage payload, which further decrypts the final payload containing the Gobinary and a vulnerable driver. 

The loader deploys and exploits the vulnerable driver to gain elevated privileges. This allows it to terminate specific antivirus applications listed in an IoC text file by creating a Windows service named KB20240815 to persist on the system.

RansomHub employed a multi-stage attack, starting with credential theft using Taskmgr.exe to dump LSASS memory and then conducting covert network reconnaissance with NetScan, laterally moving using SMB/Windows Admin Shares. 

AnyDesk served as their C&C infrastructure, while rclone was used to exfiltrate sensitive files, which leveraged various techniques to gain deep access, steal data, and disrupt operations.

A sophisticated ransomware leverages EDRKillShifter to evade security defenses and deploys a binary that encrypts files and deletes VSS snapshots.

It uses a unique file extension based on the ransom note’s filename to identify encrypted files. 

To counter this threat, organizations should strengthen endpoint protection, implement driver- and kernel-level protections, enforce credential security, enable behavioral monitoring, harden endpoint configurations, and stay updated with the latest threat intelligence.

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