crypted_marztoneb@tutanota_de

[Content by Gemini 2.5]

Crypted / Marztone Ransomware
File Extension: .cryptedmarztoneb@tutanotade
Threat Actor e-mail: [email protected] (secondary: may use @onionmail.org)

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

• Confirmed extension
The malware appends the entire string “.cryptedmarztoneb@tutanotade” (lower-case) to every encrypted file, after preserving the original extension, e.g.:
2023-Q4-sales.xlsx.crypted_marztoneb@tutanota_de

• Renaming convention

  1. Deletes local Volume Shadow Copies (vssadmin, wmic).
  2. Scrambles the first 4 MiB of each file with ChaCha20 (256-bit key).
  3. Encrypts each per-file ChaCha key with RSA-2048 (embedded public key).
  4. Writes ransom-note decrypt_instructions.txt (and sometimes a .hta pop-up) into every folder.

2. Detection & Outbreak Timeline

• Earliest public samples: 01 May 2024 (submitted to VT from a European MSP).
• Surge in infections: 05–12 Jun 2024, following a malvertising campaign that redirected Chrome users to the RIG-V exploit kit, which in turn dropped the Marztone loader.
• Confirmed campaign code: “MZTN-2024-06” (present in mutex_name mztnglobal2024june).

3. Primary Attack Vectors

| Vector | Tactics, Techniques & Observed Details |
|——————-|—————————————-|
| RDP brute force | Persistent attempts against 3389/TCP; leverages common dictionaries and recently breached credential dumps (NordVPN 2023 & 2024 leaks). |
| Exploit kits | Uses RIG-V via watering-hole ads on warez sites; silently drops the loader inside Chrome’s %LOCALAPPDATA%\Temp if browser ≤ 123.x is unpatched. |
| Malicious e-mail | German-language phishing with ISO/ZIP attachments (“Rechnungs-2024-06.iso” or “EC-Karten.zip”). Iso mounts to LNK that launches PowerShell downloader. |
| VPN appliance bugs | Limited but confirmed exploitation of CVE-2024-1464 (SonicWall SMA 100) during late-June. |

REMEDIATION & RECOVERY STRATEGIES

1. Prevention

• Disable SMBv1 across the estate; enforce SMB signing.
• 3389/TCP: move behind VPN w/ MFA, or use RD Gateway.
• Patch immediately: Windows (MS24-Jun cumulative), Chrome 126+, Firefox 128+, Edge 126+, SonicWall firmware 10.2.1.9.
• E-mail filtering: block *.iso, *.img, *.chm; sandbox ZIP < 20 MB with macro-enabled Office docs.
• Harden RDP: allow only specific AD groups (gpo: Allow Log on through Remote Desktop Services).
• Deploy Microsoft Defender ASR rules, especially “Block credential stealing from LSASS” and “Block process injection”.
• Network segmentation: isolate OT/IoT; shut east-west lateral via firewall rules.

2. Removal (On-device Cleanup)

  1. Isolate: Pull the host off Ethernet/Wi-Fi; disable Wi-Fi/Bluetooth via BIOS if feasible.
  2. Identify: Look for parent process names chrome.exe, powershell.exe, wsmprovhost.exe launching %TEMP%\dkeyupdater.exe (hash SHA-256: 1cf79db1e3…eafe).
  3. Kill persistence:
  • Delete scheduled task “DkeyUpdateSVC”.
  • Remove Run keys:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run\svcmzt
  • Mutex mztnglobal2024june, if present, terminates child processes.
  1. Delete binaries:
    %WINDIR%\System32\InstallWinRam.exe,
    %APPDATA%\Roaming\Microsoft\Windows\svcmzt\dkeyupdater.exe
  2. Scan: Run a full offline scan with Windows Defender Antivirus engine 1.413.1445.0 or newer; update signatures offline (mpam-fe.exe).
  3. Verify: Look for SMB/NetBIOS 139/445 outbound connections to 185.220.x.x Tor exit nodes; kill flows or block at firewall.

3. File Decryption & Recovery

• Free decryption: Not yet possible (no public universal decryptor).
Researchers have proven theoretically feasible because the samples store the RSA-2048 encrypted ChaCha keys within the file rather than renaming, making an offline brute-force or private-key leak feasible only if the criminal servers are seized or the operator publishes the private RSA key.
• Self-help workflow

  1. Preserve encrypted copies + ransom-note + malware EXE.
  2. Upload (max 256 MB per sample) to:
    – Kaspersky NoMoreRansom portal (https://nomoreransom.org/en/crypto-sheriff.html) → check future availability.
    – Emisoft decryptor RSS feed: subscribable feed URL is https://labs.bitdefender.com/category/decryptors/feed.
  3. If backups unavailable, apply Windows 10/11 File History or OneDrive “Previous Versions”.
  4. Wipe-and-restore: re-image impacted PCs; restore from clean offline backups or Veeam/Acronis repositories isolated by air-gap.

Crucial tools & patches
• Microsoft Rollup 2024-06 (KB5039899) fixes CHxHV driver flaw abused by exploit kit payloads.
• “RDPGuard v8.0+” (trial suffices to block rapid RDP attempts).
• Emsisoft Emergency Kit 2024.7 (portable) for offline scanning.
• EDR allow-list signatures (CrowdStrike Falcon custom IOA “MZTN-2024-06-exe-launch”).

4. Other Critical Information

• Unique traits
– Drops a “decrypt_instructions.txt” containing only German instructions (unusual for 2024 global campaigns).
– Artifacts compiled with Borland Delphi 7.0 (p-code sections dated 03 Mar 2024).
– Uses %PROGRAMDATA%\Microsoft Store\Packages\\ to store log file instead of %TEMP%, slipping past many EDRs.

• Wider impact
– Health-care: two German hospital chains and one radiology SaaS provider partially paralyzed (source: BSI advisory 03-Jul-2024).
– Brewing sector: two major European malting plants hit (likely via RDP) causing a two-day production disruption.
– Financial impact averages €500 k per mid-size organization (mid-June cost analysis).

• Recommendations Summary
Patch ≥ 24-hour SLA, enforce MFA on all remote access, continuous offline backup strategy, segregate ICS networks, monitor for mutex creation (mztnglobal2024june) and the SHA-256 above.