Description

Sophos' CTU researchers uncovered a highly advanced attack in which attackers abused the open-source Velociraptor digital forensics and incident response (DFIR) tool for unauthorized remote access. Rather than its forensically-intended use, Velociraptor was utilized to download and run Visual Studio Code, setting up a tunneling configuration to an attacker-controlled C2 server. The activity was initiated by the Windows msiexec process that installed malicious installers from a Cloudflare Workers website that hosted attack tools such as tunneling tools and Radmin remote admin tool. Remote code execution and stealthy persistence were achieved through the exploitation of Velociraptor, and attackers set Visual Studio Code as a Windows service with outputs being sent to log files for observation. CTU analysis found that such a strategy is symptomatic of a larger trend in which criminals are employing legitimate remote monitoring and management (RMM) or incident response tools as alternatives to traditional malware, making it more difficult to detect. Much of this technique is employed as an initial attack vector before the implementation of ransomware, where the attackers laterally move and exfiltrate sensitive information without infecting endpoint protection. In order to counter such threats, organizations need robust endpoint detection and response (EDR) tools that can detect process trees and tunneling behavior. Least privilege implementation, restrictive access control, and network segmentation are necessary to restrict the movement of attackers. The admins must be alerted to unusual installations of RMM or forensic software, traffic to unusual domains should be blocked, and backups should be current. Abuse of tools or unusual tunneling should be treated as high-priority incidents for enabling timely disruption of possible ransomware attacks.