Medusa Ransomware Targets Critical Infrastructure: Technical Analysis and Mitigation

The U.S. Cybersecurity and Infrastructure Security Agency (CISA), Federal Bureau of Investigation (FBI), and Multi-State Information Sharing and Analysis Center (MS-ISAC) have issued a joint advisory warning of the Medusa ransomware’s escalating attacks on critical infrastructure sectors. As of February 2025, over 300 organizations across healthcare, education, and manufacturing have been compromised, with threat actors employing triple extortion tactics and exploiting vulnerabilities like ScreenConnect (CVE-2024-1709) and Fortinet EMS (CVE-2023-48788)¹.

Technical Overview of Medusa Ransomware

First identified in June 2021, Medusa operates as a Ransomware-as-a-Service (RaaS) model, where affiliates split profits with developers. The malware employs double extortion by encrypting files and threatening data leaks, with recent cases showing triple extortion—victims who paid ransoms were later contacted by different affiliates for additional payments². Initial access is typically gained through phishing, compromised credentials, or unpatched software vulnerabilities.

Medusa’s post-exploitation toolkit includes:

Lateral Movement: PsExec, RDP, and AnyDesk for network propagation
Credential Theft: Mimikatz for harvesting credentials
Data Exfiltration: Rclone for transferring stolen data to C2 servers

Indicators of Compromise (IOCs)

Security teams should monitor for these artifacts:

Type	Example
Ransom Note	`!!!READ_ME_MEDUSA!!!.txt`
Encryptor Binary	`gaze.exe`
C2 Communication	Tor-based chat or Tox messaging

Mitigation Strategies

CISA and FBI recommend these prioritized actions³:

“Organizations should implement network segmentation to limit lateral movement and enforce multi-factor authentication (MFA) for all remote access services. Offline, immutable backups remain the most effective recovery method.”

Additional technical controls include:

Patch management for internet-facing systems, prioritizing CVEs mentioned in advisories
Endpoint detection rules to flag PowerShell obfuscation techniques
Blocking unauthorized traffic to remote services (RDP/VPNs) at network perimeters

Relevance to Security Professionals

For threat hunters, Medusa’s use of Ligolo/Cloudflared tunneling tools creates detectable network patterns. SOC analysts should monitor for base64-encoded PowerShell scripts and unexpected Rclone transfers. The ransomware’s .onion leak site ([email protected]) provides intelligence for attribution⁴.

Red teams can simulate attacks using Medusa’s documented TTPs, particularly its abuse of ScreenConnect vulnerabilities. Blue teams should test restoration procedures with the provided STIX-formatted IOCs from CISA⁵.

Conclusion

Medusa’s evolution highlights the need for coordinated defense across critical infrastructure. Organizations are advised to review CISA’s full advisory and report incidents to the FBI’s IC3 portal. The low decryption success rate (under 20% per MS-ISAC data) reinforces that ransom payments are ineffective as a mitigation strategy.