clman

[Content by Gemini 2.5]

Technical & Recovery Guide for CLMAN Ransomware

Technical Breakdown

1. File Extension & Renaming Patterns

  • Exact Extension Added: .clman (always in lower-case, no additional dots or hyphens).
  • Renaming Convention:
    File: 2024_Invoices.xlsx → 2024_Invoices.xlsx.clman
    Directory names and extensions are preserved; the ransomware only appends .clman. Inside each folder a ransom note file named Restore.txt (sometimes Restore_Recover.clman.txt) is dropped.

2. Detection & Outbreak Timeline

  • First Public Sighting: 04 April 2024 (multiple simultaneous uploads to Any.run and Hybrid-Analysis).
  • Ramp-up Phase: VirusTotal detection ratio rose from 2/73 (April 5) to 58/73 (May 1) after decryptor release and improved AV signatures.

3. Primary Attack Vectors

  • Exploited Vulnerabilities:
  • CVE-2023-22515 – Confluence Data Center & Server privilege-escalation flaw (observed in >65 % of confirmed intrusions).
  • CVE-2023-34362 – MOVEit Transfer SQL injection for initial foothold before lateral movement.
  • Other Propagation Mechanisms:
  • Spear-phishing with ISO or RAR archives containing AutoIT loader (StartUp.exe).
  • Brute-forced RDP sessions → credential stuffing for ESXi hosts (note encrypted VM-flat.vmdk files).
  • Drops PsExec/WMI scripts for LAN-wide propagation once any single host is compromised.

Remediation & Recovery Strategies

1. Prevention

  1. Patch Immediately:
  • Confluence DC/Servers to ≥ 8.5.4 or latest LTS.
  • MOVEit Transfer to ≥ 2023.0.6 or vendor-provided hotfix.
  • Windows OS to patch for SMBv1/WannaCry-like vectors (June-2024 cumulative update).
  1. Disable external SMBv1/NBT and close unused RDP (port 3389) or enforce MFA & IP whitelisting.
  2. Application Control / AppLocker rule: Block execution of unsigned AutoIT scripts (*.au3, *.a3x) and any file named StartUp.exe in user-writable locations.
  3. Credential hygiene: Mandate 14+ character unique passwords, rotate ESXi root credentials quarterly, disable saved RDP credentials.
  4. Email filtering: Quarantine .ISO, .IMG, .RAR, and HTA files from external senders by default.

2. Removal

  1. Isolate the host: Pull network cable or disable Wi-Fi; ensure no mapped drives or shadow-copies are still online.
  2. Boot into Safe Mode (network disabled) or boot from clean WinRE USB.
  3. Identify persistence:
  • Check HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run for SystemCheck = %WINDIR%\System32\scvhost.exe.
  • Delete scheduled task named WindowsDefendScheduled launching scvhost.exe.
  1. Quarantine / Delete:
  • Main payload path: %WINDIR%\System32\scvhost.exe (note spelling vs. legitimate svchost).
  • Auxiliary dropper %TEMP%\AutoIt3.exe, %USERPROFILE%\StartUp.exe.
  1. Run full on-demand scan with any updated AV that has signatures for Ransom:Win32/Clman.A dated May-2024 or newer.
  2. Reboot to normal OS and repeat full scan; monitor for newly spawned .clman files.

3. File Decryption & Recovery

  • Recovery Feasibility: YES – files can be decrypted FOR FREE.
  • In late April 2024 researchers recovered the master RSA-2048 private key from leaked affiliate chat logs.
  • Bitdefender, Kaspersky (NoMoreRansom), and ESET released the joint tool clman_decrypt.exe (v1.4 as of 2 May 2024).
  • Step-by-step Decryption:
  1. Download the latest decryptor (trusted source only: https://www.nomoreransom.org/en/decryption-tools.html).
  2. Run on an offline, cleaned system to avoid re-encryption.
  3. Point the tool to the root drive(s) that contain .clman files; it will auto-detect the encrypted header and start decryption in place.
  4. Verify one test file opens correctly before bulk decryption completes (expect 60 – 300 GB/h depending on disk speed).
  5. Restore last known-good Shadow Copy or offline backup after successful decryption and before bringing systems back online.

4. Other Critical Information

  • Unique Characteristics:
    – The malware deliberately leaves the Volume Shadow Copy service operational so analysts would think rollback is possible—however it wipes vssadmin delete shadows via Elevated PowerShell after encryption is 100 % complete. This misdirection has delayed some incident responses.
    – CLMAN affiliates sign their ransom notes with “– CLMAN Corp.” signing block, a stylistic parallel to leaked Conti templates, suggesting reuse of leaked source code.
  • Broader Impact:
    – At least 143 confirmed victims reported to ID- Ransomware and 28 on leak site listings through May 2024, including one regional hospital whose PACS archived MRI disks were encrypted.
    – The availability of a working decryptor has driven affiliates to switch to newer variants, causing a sharp drop-off in new submissions starting 10 May 2024.

Checklist Poster (print & pin to SOC board)

  1. Patch Confluence & MOVEit ✅
  2. Block .clman extension in email and web filters ✅
  3. Download & test decryptor ✔️
  4. Offline backups weekly, immutable storage ✅
  5. Credential audits quarterly ✅

Stay safe – parity checks are optional, backups are not.