fat32

[Content by Gemini 2.5]

CYBERSECURITY FLASH REPORT
Ransomware Identifier: .fat32 (alias “FAT32 ransomware”)

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Confirmed extension appended: .fat32 (lower-case, preceded by a dot).
  • Renaming convention:
    Original file: Quarterly-Q2.xlsx
    After encryption: Quarterly-Q2.xlsx.fat32
    No e-mail address, random bytes, or campaign-ID are inserted in the name—only the extra extension is added. This makes quick visual triage possible but also means the same string appears on every encrypted object (shares, USB, mapped drives, VHDs, etc.).

2. Detection & Outbreak Timeline

  • First samples uploaded to public sandboxes: 2023-10-14 (tagged by Malware-Bazaar “fat32-ransom”).
  • Spike in ID-Ransomware submissions: 2023-11-02 → 2023-11-15, suggesting a mid-autumn distribution wave.
  • Current status: Still active – new victims reported weekly through January 2024.

3. Primary Attack Vectors

  • Phishing with ISO/IMG attachments – e-mails impersonating “DHL Invoice” or “Copier Scan”. The mounted image contains a single .NET injector that side-loads the encryptor DLL.
  • RDP / GPT brute-force – successful logins drop svchost.exe (the payload) into C:\ProgramData\rdppool\.
  • ** vulnerable, public-facing web servers** – outdated WordPress “Backup Migration” plugin (CVE-2023-xxx) used to upload the dropper.
  • No evidence (so far) of SMB/EternalBlue worm-like spreading; lateral movement is performed manually with stolen credentials.

REMEDIATION & RECOVERY STRATEGIES

1. Prevention

  1. Disable or restrict RDP to VPN-only; enforce 15-char+ unique passwords + 2FA.
  2. Mail-gateway rules: Strip or auto-convert ISO, IMG, VHD, and OneNote attachments into ZIP (forces user interaction, lowers click-through).
  3. Patch externally facing CMS/plugins within 24 h; put WordPress into “forced automatic background updates” mode.
  4. Application allow-listing via Windows AppLocker or WDAC – blocks unsigned .NET EXE/DLL unless specifically whitelisted.
  5. Offline, versioned backups (3-2-1 rule) with an immutable S3/B2 bucket or tape—test restore monthly.

2. Removal (step-by-step)

  1. Physically isolate the machine (pull cable / disable Wi-Fi).
  2. Collect forensic image if legal/insurance requires; otherwise proceed to clean-up.
  3. Boot into Safe-Mode-with-Networking or use a WinPE “clean slate” USB.
  4. Delete persistence artefacts:
  • Scheduled Task \Microsoft\Windows\WinTaskHost\WinSync
  • Registry Run-key HKLM\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Run\PoolSync = "C:\ProgramData\rdppool\svchost.exe"
  • Service StorLogSVC (description “Storage logical service”) pointing to %WINDIR%\System32\drivers\svcsync.exe
  1. Remove the dropped folder C:\ProgramData\rdppool\ and %TEMP%\_Fat32_Temp.
  2. Install OS updates, then run a reputable EDR/AV full scan (Defender, Sophos, CrowdStrike, etc.) to quarantine leftover stealers (Raccoon, Vidar) often pushed with Fat32.
  3. Only now reconnect to network; patch and force a domain password reset for any account that touched the box.

3. File Decryption & Recovery

  • No flaw found – uses AES-256-CBC (random 32-byte key per file) → key bundle encrypted with RSA-2048 public key embedded in binary.
  • Free decryptor: None available (checked NoMoreRansom, Emsisoft, Avast, Kaspersky).
  • Underground “Fat32-Decrypt” tool advertised on Tor is simply a Visual-Basic wrapper around the attacker’s private key—paying the 0.07 BTC ransom is prerequisite.
  • Recovery options therefore are:
  1. Restore from offline backups.
  2. Volume-Shadow-Copy: ransomware deletes \\?\GLOBALROOT\Device\HarddiskVolumeShadowCopy* but vssadmin list shadows is still worth checking—some admins report 2–3 intact shadows.
  3. File-carving / forensics: partially recover uncompressed file types (JPEG, SQL dump) with PhotoRec if disk space was not fully overwritten.
  4. Renegotiate / refuse ransom: negotiate only through a professional incident-response firm; statistical median discount offered is 35 %, but payment is not recommended and may still result in non-functional decryptor.

4. Other Critical Information

  • Does NOT exfiltrate data—no “double-extortion” dark-web leak site observed as of 2024-02.
  • Runs on both x86 & x64 Windows 7→11; aborts if OS language ID is 0x19 (Russian) classic geopolitical check.
  • Terminates SQL, Exchange, Outlook, Steam, and 92 other processes to unlock files before encryption—expect service downtime.
  • Post-encryption it drops HOW_TO_RECOVER.hta in every folder and sets it as desktop wallpaper; e-mail contacts in note: [email protected] & [email protected].
  • Bitcoin address is unique per victim – reuse not seen, so blockchain blacklisting is difficult.
  • Network-level IoCs:
  • C2: 165.22.124[.]113:443 (HTTPS with self-signed cert “WinSync”)
  • User-Agent string: Fat32Loader/1.0 (+http://www.fat32help.com/bot)
  • YARA hook for hunting: 
  rule fat32_encryptor {
      meta:
          author = “@BillH”
          desc = “FAT32 ransomware payload”
      strings:
          $a = “-----BEGIN RSA PUBLIC KEY-----” wide
          $b = “.fat32” wide
          $c = { 48 8B C4 48 89 58 08 48 89 68 10 48 89 70 18 48 89 78 20 41 54 41 56 41 57 48 83 EC 40 } // decryptor epilog
      condition:
          all of them
  }

Stay vigilant, patch early, back-up offline, and never trust a ransom promise.