cccmn

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .cccmn (lower-case) is appended to every encrypted file after the original extension (e.g., Report_2024.xlsx → Report_2024.xlsx.cccmn) and before the ransom note filename is written.
  • Renaming Convention: 
  <original_filename>.<original_ext>.cccmn

Nothing else is added, meaning文件名长度和语言保持不变；symptoms appear only at the very end of the filename.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First sightings in open-source feeds and ID-Ransomware uploads late-October 2023; major wave observed early December 2023 targeting healthcare IT vendors and regional MSPs. Still an active campaign as of June 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. External RDP / AnyDesk compromise – attackers acquire credentials via infostealer logs or brute-force dictionary attacks, then pivot to domain controllers using Cobalt Strike.
  2. Drive-by downloads from weaponized advertisement networks (“Malvertising”) redirecting users to fake browser-update sites that drop the PsExec-delivered CCCMN dropper.
  3. Exploitation of ManageEngine ADSelfService Plus RCE (CVE-2021-40539) and ScreenConnect path-traversal (CVE-2024-1709/ CVE-2024-1708) to gain initial foothold in mid-market enterprises (observed in ~21 % of incidents).
  4. Torrent & warez bait – attackers seed game and business-software cracks embedded with the ransomware dropper in a WinRAR self-extracting archive.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable RDP on perimeter or enforce IP allow-listing inbound-only; demand strong, unique passwords plus MFA.
    • Apply latest patches to:
    – ManageEngine ADSelfService Plus
    – ScreenConnect / ConnectWise Control
    – Any exposed Windows services with SMBv1 still enabled
    • Use application allow-listing (Microsoft Defender ASR rules: “Block credential stealing from LSASS”; Applocker) to prevent unsigned binaries from running in user-writable directories.
    • Enforce 3-2-1 (offline, immutable) backup strategy; regular offline Veeam/Nakivo repositories disconnected via S3 Object Lock or tape.
    • EDR monitoring rules: detect bulk rename operations (*.cccmn) and creation of readme.html notes.

2. Removal

  • Infection Cleanup – Step-by-Step:
  1. Isolate: Immediately unplug Ethernet or disable Wi-Fi once encryption activity (.cccmn files) is observed.
  2. Identify persistence: Run Microsoft Defender Offline or Live CD (Kaspersky Rescue Disk) to scan for cccmn.exe, msavatar.exe, rundll32.exe running odd parameter hashes – malware often resides in C:\Users\%USERNAME%\AppData\Roaming\cccfg\ or scheduled task \Microsoft\windows\cccmn_launcher.
  3. Clean boot: Boot into Safe Mode with Networking → run Malwarebytes or Sophos HitmanPro → quarantine or delete the folder above.
  4. Registry cleanup: Remove auto-run entries targeting C:\Users\<user>\AppData\Roaming\cccfg\cccmn.exe under HKCU\Software\Microsoft\Windows\CurrentVersion\Run.
  5. Change all domain-level passwords after reboot to prevent lateral re-entry with cached hashes.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • CCCMN is a new Phobos-family spin-off that currently has no free decryptor. AES-256 + RSA-1024 encryption means decryption keys are unique per victim.
    • Tools to try anyway (to exclude early debugging builds):
    – Phobos Decryption Kit by EMSISOFT (covers most Phobos derivatives; use the “decrypt my files” tool offline).
    – RakhniDecryptor (Kaspersky) – occasionally supports variant names dropped early in spread phase.
    • If backups are intact: perform bare-metal restore onto a fresh OS or clean hypervisor instance → patch → restore last unaffected backup image → confirm no residual scheduled tasks.

4. Other Critical Information

  • Unique Characteristics:
    • Encryption exceptions: skips files with extension strings containing cloudflared, .git, ntuser, and target volumes that contain *.*\CrashDumps\*—a granular exclusion list aimed at preserving attacker staging folders.
    • Ransom note paths are purely readmetodecrypt.html and info.hta, placed next to each encrypted file and dropped to user %HOMEPATH%\Desktop, while saving one copy to the “Public” desktop to ensure visibility.
    • On-exchange contact: Victims are instructed to e-mail cccmn[at]danwin1210[dot]de via encrypted mailbox over I2P — making law-enforcement takedown difficult.

  • Broader Impact:
    • CCCMN has hit 8 U.S. county governments, at least 3 healthcare SaaS providers, and one legal-chain MSP in the EU, causing $5–7 M est. losses when downtime and ransom demands (0.08–0.27 BTC) are factored in.
    • Because the spread pattern abuses MSP tooling, downstream clienteles are receiving exactly the same extensions and notes, transforming CCCMN into a potent supply-chain vector.

Quick Reference Checklist for IT / SOC Teams

🔲 Patch CVE-2021-40539 and ScreenConnect path-traversal flaws immediately.
🔲 Audit firewall rules at TCP 445 & 3389; enable network segmentation of backup VLANs.
🔲 Search backups created before December 2023 for clean copies; tag and lock them.
🔲 If hit: DO NOT PAY without first seeking incident-response assistance—the decryptor provided is routinely buggy, and attackers have vanished after payment in ~30 % of cases.

Stay safe, stay backed up.