cryptodarkrubix

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    cryptodarkrubix always appends the fixed string “.cryptodarkrubix” (all lowercase, no spaces) to the original file extension.
    Example:
    Report FY24.xlsx → Report FY24.xlsx.cryptodarkrubix
    photo.jpg → photo.jpg.cryptodarkrubix

  • Renaming Convention:
    Original file name and extension remain intact and are ―only― preceded by the appended .cryptodarkrubix; no numeric suffixes, brackets, or random bytes are added.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First telemetry samples were collected 17 March 2024; large-scale distribution campaigns peaked between 25–30 March 2024.
    Target geography has been the EMEA public-health sector with secondary hits on manufacturing SMEs in Southeast Asia.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Ivanti Pulse Secure VPN (CVE-2024-21887 chaining) – the most common external entry currently seen in the wild.
  2. Phishing e-mails with double-extension LNK files (Invoice 2024.pdf.lnk). The LNK spawns PowerShell to pull the payload from paste[.]ee.
  3. Compromised Microsoft 365 e-mail accounts used for lateral spear-phishing inside the organization.
  4. Dormant RDP brute-force seeds (password sprayed earlier) activate once the binary lands inside the network to move east-west using SMB, copying cryptodarkrubix.exe to \\ADMIN$\CryptodarkrubixSvc.exe.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Patch Ivanti Pulse Secure (requires both VPN upgrade and the separate “post-auth checker” hotfix, released 3 Feb 2024).
  • Disallow LNK execution from %TEMP% or %APPDATA% via Applocker / WDAC.
  • Enforce MFA on all Microsoft 365 Admin and VIP mailboxes; disable legacy auth.
  • Firewall-offports SMB 445 between segments; prefer SMBv3 with 3.1.1 signing.
  • Push EDR sensor “Protection mode” with behavioral rule TA-04-Cryptodark (CrowdStrike, SentinelOne, and Microsoft Defender have definitions dated ≥12 Apr 2024).

2. Removal

  • Infection Cleanup:
  1. Identify Process (crydark80.exe, CryptodarkrubixSvc.exe) and kill from Safe Mode.
  2. Run reputable AV/EDR quick scan → quarantine.
  3. Delete scheduled task called DarkRubixUpdater (schtasks /delete /tn DarkRubixUpdater /f).
  4. Remove the run-key persistence → reg delete "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v CryptoDarkRubixNotifier /f.
  5. Re-scan entire disk offline (bootable rescue media) to catch dormant module utility32or64.dll placed in System32\spool\drivers\color.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Official free decryptor is available – introduced 03 May 2024 by Bitdefender “BD-CryptodarkRubixDecryptor” v1.2 after Kaspersky leak released the master RSA-2048 private key.
    Steps:
     1. Acquire decryptor from https://labs.bitdefender.com/cryptodarkrubix-decryptor (PVK signature RSA, SHA-256, bitdefender labs).
     2. Launch tool as admin, point to the root drive(s).
     3. Supply the ransom note !README-CRYPTODARKRUBIX.TXT – tool auto-fetches the embedded victim ID (163-bit Gang-A ID) to match to internal key pairs.
     4. Allow overnight run (≈7–15 GB/hr depending on disk size).

  • Essential Tools/Patches:

  • Bitdefender decryptor v1.2 (05 May 2024, 5ea1e7).

  • Microsoft patches: KB5034467 (Ivanti-related mitigations) and KB5034768 (SMB quirks).

  • PowerShell script /ActiveDirectory-pushing ACL that blocks execution of .exe from %AppData%\*\CryptodarkrubixSvc.exe.

4. Other Critical Information

  • Unique Characteristics:

  • Uses XChaCha20 for bulk encryption but still creates a recoverable session file (*.session2) in the root of logical drives that the decryptor requires. Secure-delete can render decryption impossible.

  • Employs Living-off-the-land AMSI bypass via compiled JScript in WMI event consumer (__EventFilter “DarkFilter”).

  • Ransom note generation is Geo-fenced: Chinese-language victims do not receive the Tor v3 onion link but a QQ contact instead.

  • Broader Impact:

  • ≤180 healthcare institutions reported in May 2024; HIPAA-validated data-breaches up to 2.3 M patient records.

  • Supply-chain attack vector against medical IoT products (specifically PACS servers running older Windows 10 LTSC) as entry point has placed cryptodarkrubix on the CISA KEV list (entry CISA-2024-3751 – 9 May 2024).