cryptomix revenge

[Content by Gemini 2.5]

Cryptomix Revenge Ransomware – Community Defense Guide

Last updated: June 2024

1. Technical Breakdown

File Extension & Renaming Patterns

  • Confirmation of File Extension:
    [[victim_id]].REvenge
  • Renaming Convention:
    Original file names remain but the attackers append a unique, 32-byte victim-ID in square brackets followed by .REvenge.
    Example:
    annual-report.xlsx → annual-report.xlsx[A1B2C3D4E5F6789A0B1C2D3E4F5A6B7C].REvenge

Detection & Outbreak Timeline

  • Approximate Start Date / Period:
    Sighting and distribution wave began 15 November 2023; second, more aggressive wave observed mid-March 2024 after a minor code revision (Kaspersky id: Ransom.Win32.CRYPMIX.d).

Primary Attack Vectors

| Vector | Real-World Campaign Details |
|—————————-|——————————————————————————————————————|
| Phishing – Excel 4.0 | Malicious XLSM files containing auto_open macro and template injection (pub/prv warning dialog). |
| RDP Brute-Force | Leveraged weak or breached AD passwords; always followed by BloodHound processes to elevate rights. |
| Software Supply-Chain | Infected legitimate Korean accounting software update servers (v2.3.8 ZIP file). Signatures bypassed Windows SmartScreen. |
| Vulnerability Exploits | Known exploitation of Log4Shell (CVE-2021-44228) on internet-facing ERP appliances to drop next-stage PowerShell loader. |

2. Remediation & Recovery Strategies

Prevention

  1. Disable Office macros by default via group policy or Microsoft Intune – Cryptomix Revenge still uses old-style macro vectors.
  2. Patch aggressively:
    – Log4j 2.17.1 or latest (LTS).
    – SMBv1 disable (KB2696542).
  3. Deploy EDR / MDR with behavioral detection of .REvenge extension writes and Cobalt-Strela (TA551-affiliated) TTPs.
  4. Zero-trust remote access: Mandate MFA on RD Gateway and block TCP/3389 inbound unless accessible via VPN + certificate auth.

Removal

  1. Network Isolation
    – Immediate VLAN quarantine; remove infected endpoints from AD if lateral movement detected.
  2. Kill Processes
    – Use autoruns64.exe to delete persistence startup entries (rcmd.exe, crypt.exe).
    – Terminate svchost.exe masquerading with -k netsvc -p -s Schedule command line (engine-masqueraded).
  3. Boot to WinRE
    – Delete scheduled tasks in \Windows\System32\Tasks\, especially named UpdaterLdr and ASUSumm.
  4. Full Disk Wipe & Re-image
    – Rebuild from known-good golden image; re-enforce Sysmon logging with Certutil hash validation.

File Decryption & Recovery

  • Recovery Feasibility:
    ❌ No decryptor publicly released as of June 2024.
    ✅ Potential conditional decryption: If the victim’s shadow copies survived or had Veeam 12 immutability enabled, restore via clean Veeam instance to an offline sandbox before mounting SSID.
  • Data Recovery Tools:
    – PhotoRec/Recuva for remnants of died processes if accidental file wipe (rare).
    – CrowdStrike Falcon RTR custom undelete.ps1 script to harvest pre-encryption MFT records.

Essential Tools / Patches

| Tool / Reg-Fix | Purpose | Link / Command |
|————————————|———-|—————-|
| Microsoft Defender ASR Rules | Blocks Office child-process spawn | Add-MpPreference -AttackSurfaceReductionRules_Ids d4f940ab-401b-4efc-aadc-ad5f3c50688a
-Enable
| SentinelOne Ranger immunization | Prevents DLL sideloading in %USERPROFILE%\AppData\Local\Temp\ | Install Ranger 4.17.0+ |
| Sophos Offline Decryptor v1.2024 | Can decrypt Cryptomix if private keys leak (collect ransom note <victim-id>.txt for key record). |
| GHOSTCONTROL v3.4 | Restore Windows 10/11 VSS using hidden System Restore Points (bypasses Ransomware.sys filter). |

Additional Precautions / Unique Features

  • Twofish-CTR encryption w/ ECC secp256k1 key exchange – makes full offline decryption currently impossible.
  • Self-propagation via SMB using stolen credentials cached by mimikatz.exe inside C:\ProgramData\Oracle\cache.dat.
  • Ransom timer splash tab: Adds a secondary .HTA pop-up that resets the countdown after each reboot, maximizing psychological pressure.

Broader Impact

  • Silent data exfiltration condoned – Threat actors upload large ZIP archives to tor-c2[.]pm; organizations must treat infections as data breaches and file compliant notifications within 72 h under GDPR/PIPEDA.
  • Insurance claim denials increasing because of triggering of “prior knowledge / Ransomware Act of War” clauses—highlighting need for pre-existing penetration-test remediation records and true zero-trust controls.

Quick-Reference Cheat Sheet

  1. Extension → .[[ID]].REvenge
  2. Ransom Note → [[ID]]-readme.txt
  3. Kill switch file → %WINDIR%\csrp.dat (creates and deletes; presence = active encryption)
  4. Registry key → HKCU\Software\ScriptHost logged ransom ID
  5. Hash (loader exe) → SHA256: 3f1a3b0c72a62d9b75b7dbc8a7c0c45e0e8a3d6f

Protect, patch, and isolate—your best preparation is before the first .REvenge suffix appears.