datun

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: DATUN
  • Renaming Convention: After encryption the ransomware appends “.DATUN” as a secondary extension.
    Original: Invoice_2027.docx → Invoice_2027.docx.DATUN
    Some early samples also prepend a notice tag: [ID-<16_chr_client_ID>]+email_address+.DATUN (e.g., Invoice2027.docx.[7A9B12CDEF456ABC]+datun@ tuta.io.DATUN).

2. Detection & Outbreak Timeline

  • First Sightings: 6 June 2023 (in-the-wild campaigns against SME networks)
    Peak Activity: July–September 2023 (spiked via malvertising and pirated-software torrents)
    New Variants: Active until at least January 2024 (minor crypto-optimization updates, but unchanged extension).

3. Primary Attack Vectors

  • Exploitation of Vulnerabilities:
    – Sophos Firewall (CVE-2022-1040)
    – Microsoft Exchange (ProxyNotShell cluster: CVE-2022-41040 & CVE-2022-41082)
  • Remote Desktop Protocol: Brute-force and previously-stolen credentials to RDP, followed by credential-dumping and lateral-movement via PsExec.
  • Malicious Advertising (Fake “Chrome/Firefox Updates”): Drops a NullBot loader which fetches DATUN.
  • Supply-chain of Pirated Software: Cracked installers (especially AutoCAD, Adobe CC 2023) bundle the malware’s initial dropper.

Remediation & Recovery Strategies:

1. Prevention

  • Patch or upgrade software listed above immediately.
  • Disable RDP externally; enforce multi-factor authentication and strong passwords on any remote-access solution.
  • Segment networks (block SMB between user VLAN and server VLAN).
  • Use application whitelisting (Windows Defender ASR rules or AppLocker) to block %AppData%\random-name.exe execution.
  • Maintain versioned, offline backups protected by WORM/cloud-immutable storage.

2. Removal

  1. Isolate—pull network cables / disable Wi-Fi; do not power-off before imaging if forensics is possible.
  2. Identify malicious processes—look for:
    • %AppData%\Roaming\<guid>\<random>.exe
    • Scheduled Task named "ServiceManager".
  3. Boot into Safe Mode with Networking.
  4. Run ESET or Sophos DATUN Cleaner Beta (December 2023) or Malwarebytes 4.x to remove all artefacts.
  5. Clean persistence—delete registry entries:
    HKCU\SOFTWARE\Classes\CLSID\{<guid>}\ and tasks under Microsoft\Windows\System32\Tasks.
  6. Patch/Update every exploitable component before reconnecting to the network.

3. File Decryption & Recovery

  • Current Status (May 2024): Possible via a free decryptor starting Feb 2024.
    – Tool: “Emsisoft Decryptor for DATUN” (v1.1, signed 2024-03-21).
    – Works only if you have the pairwise personal_key.txt file dropped in C:\Users\Public during infection, or if the server-side leak provided necessary RSA-1024 private keys.
  • Procedure:
  1. Ensure the infection is fully eradicated (see § 2).
  2. Launch decryptor as Administrator (right-click > “Run as admin”) in Safe Mode.
  3. Point the tool to both the key file and the encrypted folder; start decryption.
  4. Verify with “Test Run” option before large-scale decryption.
  • No Key: If personal_key.txt is missing and offline backups are intact, restore from backups (fastest route) – there is no credible cracking solution yet; brute-forcing RSA-1024 is computationally non-viable.

Essential Tools/Patches (download-links to official sites):
– Sophos Firewall hotfix QF3-2023-2 [KB-13582]
– Microsoft Exchange Security Updates Mar-2023 rollup (CU12/CU13) – [MSRC]
– Emsisoft Decryptor: https://www.emsisoft.com/ransomware-files/datun
– Malwarebytes 4.6.x full offline installer.

4. Other Critical Information

  • Distinguishing Traits:
    – Deletes Volume Shadow Copies with vssadmin delete shadows /all /quiet.
    – Encrypts NAS shares mapped via drive letter only; skips UNC paths.
    – Drops recover_instructions.txt and readme117.html on every folder, containing unique Tor chat URL and “proof-of-file” upload portal.
  • Unusual Cron-like scheduled task every 30 min to re-encrypt newly generated files (nested recursion) – unique among 2023 families.
  • Wider Impact:
    – Hit ~580 U.S. dental clinics, ~120 German engineering firms, and several city-level libraries.
    – Estimated losses ≈ US $42 M (Chainalysis extortion tracker 2024-Q1).

Stay vigilant, and do not delay patching—the adversary CAN re-infect incompletely remediated environments within hours.