BlackMesh Ransomware Group Pivots to Healthcare Infrastructure

Threat Overview

Threat intelligence firm DarkLens has released a detailed report on BlackMesh, a ransomware-as-a-service (RaaS) group that has dramatically increased attacks on healthcare organizations since Q4 2023.

The group is believed to operate from Eastern Europe and has claimed responsibility for breaches at 14 hospitals and three pharmacy chains over the past 90 days.

Initial Access Vectors

BlackMesh affiliates are primarily using two initial access methods:

1. Citrix Bleed (CVE-2023-4966)

The group has been observed mass-scanning for vulnerable Citrix NetScaler instances exposed to the internet. Once access is obtained, they hijack existing authenticated sessions and move laterally within the victim network.

2. Stolen VPN Credentials

Credentials purchased from initial access brokers on dark web forums have been used to gain footholds in at least six confirmed healthcare incidents. Multi-factor authentication bypass via MFA fatigue attacks has been documented in two cases.

Tactics, Techniques & Procedures (TTPs)

Phase	Technique	MITRE ATT&CK
Initial Access	Valid Accounts (VPN/Citrix)	T1078
Discovery	Network Scanning	T1046
Lateral Movement	Pass-the-Hash	T1550.002
Exfiltration	Rclone to cloud storage	T1567.002
Impact	Data Encrypted for Impact	T1486

Indicators of Compromise (IoCs)

C2 Infrastructure:

185.220.xxx.xxx (Tor exit node relays)
blackmesh-leaks[.]onion

File Hashes (SHA-256):

a3f1b2c4d5e6f7890abc123def456789...  (encryptor binary)
9876fedc ba5432100fedcba9876543210...  (credential stealer)

Recommendations for Healthcare Organizations

1. Patch Citrix NetScaler — Apply CVE-2023-4966 patches immediately and revoke all active sessions post-patch.
2. Enable phishing-resistant MFA — Deploy FIDO2/WebAuthn to prevent MFA fatigue attacks.
3. Segment OT/clinical networks — Isolate medical devices and clinical systems from corporate IT.
4. Test offline backups — Ensure air-gapped backups exist and have been recently verified restorable.
5. Deploy EDR on all endpoints — Prioritize coverage for servers and privileged workstations.