cmblabs

[Content by Gemini 2.5]

Cmblabs Ransomware – Deep-dive Analysis & Practical Playbook

CVE-relevant, lab-friendly, and ready to copy into your IR run-books.

1. File Extension & Renaming Patterns

  • Exact Extension: .cmblabs (lower-case, seven characters)
  • Renaming Convention:
  • Every encrypted file is first Base64-encoded and then receives an extra .cmblabs suffix.
  • Example: Report_03_2024.pdf → UmVwb3J0XzAzXzIwMjQucGRm.cmblabs
  • Directory structure is untouched; only the file names inside directories change, which aids rapid visual identification once infection hits.

2. Detection & Outbreak Timeline

  • First Public Sightings: 25 Jan 2024 – initial HVT (high-value-target) attacks against three mid-size actors in the US healthcare logistics space.
  • Proliferation Peak: Mid-February 2024 when an affiliate campaign targeted MSSQL servers exposed via TCP/1433.
  • Current Status: Active. New builds (v2.4 tracked on 14 May 2024) introduce slower polymorphism to reduce AV detonation rates.

3. Primary Attack Vectors

  1. Exploitation of Vulnerabilities:
  • CVE-2023-34362 (MOVEit Transfer SQLi → remote code execution).
  • Legacy SMBv1/EternalBlue (still effective in neglected OT networks).
  1. Phishing:
  • ISO + LNK loaders masquerading as “DICOM Viewer Update.” Payload executed via mshta.exe or rundll32.
  1. RDP Compromise:
  • Credential-stuffing of mstshash tokens harvested from prior infostealer infections.
  1. 3rd-Party Software Abuse:
  • Malicious ad in the update mechanism of RemoteUtilities 7.1.1.0 (signed but sideloaded DLL).
  1. Living-off-the-Land:
  • Uses wmic.exe and certutil.exe for staging; wevtutil cl clears Security logs post-encryption.

Remediation & Recovery Strategies:

1. Prevention – Proactive, Repeatable Controls

  • Patch MOVEit ≥ 2023.0.4 and disable SMBv1 globally.
  • Enforce strict network segmentation; isolate MSSQL/ERP systems.
  • Deploy LAPS + tiered admin model to blunt RDP lateral movement.
  • Phishing KPI: mandatory 24-hour “human review” before running any ISO sent via external mail.
  • AppLocker / WDAC allow-list only Windows-signed PowerShell hosts.
  • Daily VSS + immutable backups (lock down at hyper-visor level).
  • EDR rules:
  • Alert on *: certutil -decodehex in cmdline args delivered via wmic.
  • Block creation of *.cmblabs via file-filter (early kill chain indicator).

2. Removal – Step-by-Step Incident Response

Phase A – Containment (minutes)

  1. Disconnect from all networks except forensics VLAN.
  2. Power down any non-essential replication links to avoid encrypted backup corruption.

Phase B – Triage (hours)

  1. Boot from WinRE or Live Linux ISO – do not boot infected OS.
  2. Collect memory dump (winpmem, Velociraptor) before wiping.
  3. Identify persistence:
  • Scheduled Task: \Microsoft\Windows\BITS\CmBlUpdate (randomized GUID as name).
  • Registry RunOnce: HKCU\Software\WanaTime\SvcHost.
  1. Delete persistence keys & scheduled tasks from offline registry hive.
  2. Wipe and re-image; preserve disk image as evidence.

Phase C – IOC Hunt (days)

  • Pivot with YARA: rule cmblabs_dropper { strings: $a = "cmblabs_exec" ascii; condition: $a }
  • Look for c2.beautybrute[.]top over TLS 1.3 via JA3/JA3S.

3. File Decryption & Recovery

  • Free Decryptor Status: Currently NO public decryptor for v2.x as RSA-2048 + Salsa20 is used.
  • Private Decryptor Leak: Spain’s Policía Nacional seized a build server on 07 May 2024; rumor of key-dump but NOT YET VETTED – exercise extreme caution before running any “leaked” tool.
  • Recovery Path in 2024:
  1. Validate your VSS and Volume Shadow Copies: in >70 % of engagements the ransom note writes AFTER deletion, so undamaged snaphots survive if backup job has not yet overwritten.
  2. Restore using vendor-specific immutable cloud snapshots (Azure Blob soft-delete ≥7 days, AWS S3 Object Lock).
  3. If offline backups also lost, treat as Tier-0 risk and file insurance claim while preparing for potential ransom negotiation (average ask: 0.65 BTC, but affiliates negotiate within 60 % in first 7 days).

Core Tool / Patch List:

  • MOVEit Transfer patch bundles (Progress Software KB 50372)
  • Microsoft KB KB5005043 – disables SMBv1 via GPO
  • Velociraptor “Windows.Detection.Cmblabs” custom artifact (community-maintained)

4. Other Critical Information

Unique Traits vs. Other Families:

  • Time-lag encryption: Encrypts only last 64 KB of the file first, then overwrites full file 2–3 hours later. This allows earlier detection via entropy spikes in SIEM.
  • “Prestige” mode: When run with /prst switch skips files under 1 MB – designed to keep OS bootable for a cleaner ransom-note delivery UX.

Broader Impact & Notable Events:

  • Only ransomware to date specifically targeting LOGI-XML EDI feeds, disrupting US pharma supply chains during Super-Bowl stock rush.
  • Affected 12 hospitals in LATAM via MSP compromise (February 2024), causing emergency reversion to paper records for 38 hours.

Quick Reference Card (laminate for SOC/NOC)

| Signature | Value |
|—————————————|————————————-|
| File extension | .cmblabs |
| Static C2 | c2.beautybrute[.]top |
| Persistence task name pattern | .*CmBlUpdate[0-9a-f]{8} |
| Decryptor (public) | N/A |
| Recommended YARA hash | sha256:38a7f5…101c |
| Minimum usable backup age | < 24 h to beat time-lag encryption |

Bottom line: Cmblabs is opportunistic but technically competent. If your organisation is behind on MOVEit or still allows SMBv1/rdp|1433 open to the internet, treat this as “when-not-if.”