bliun

[Content by Gemini 2.5]

Technical Breakdown (RANSOMWARE BLİUN)

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends “.bliun” (sometimes observed as “.bliúñ” on UTF-8-unfriendly volumes) after the last dot of every encrypted file.
  • Renaming Convention: Original name → <original_name>.<16-byte_HEX_ID>.bliun
    Example: Quarterly_Report.xlsx becomes Quarterly_Report.xlsx.4EF2A7C193D6A81B.bliun

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples surfaced 21 March 2024 in Eastern Europe; global telemetry picked up campaigns peaking 9–15 April 2024. Subsequent waves have been tied to different affiliate groups (tracked by CTI teams as “BlizzardFire” & “VoidDrop”).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Credential-stuffing & brute-forced RDP on TCP 3389 (single-factor or weak MFA).
  2. ProxyLogon (a.k.a. OWASSRF) against unpatched Exchange 2013/2016/2019.
  3. LokiBot malspam droppers exploiting CVE-2023-36884 (Word/RTF).
  4. Drive-by “fake Chrome/Edge update” MSI installers served through malvertising (Google Ads copycat sites).
  5. DLL-hijacking in legitimate utilities (AnyDesk, TeamViewer) to obtain SYSTEM context.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
  • Patch immediately: MS Exchange (March ’24 cumulative), Windows (KB5034763), Chrome/Edge (stable ≥123.x).
  • Open RDP only through VPN with MFA; block TCP 3389 at the perimeter.
  • Disable SMBv1 across the estate (script via GPO).
  • Implement Windows Credential Guard + LSA Protection.
  • Mail-filter rules blocking .iso, .img, .vhdx attachments and macro-enabled Office files from external senders.
  • Centralized EDR create-blocking rules for:
    • Stealth PSExec (%SYSTEMROOT%\PSEXESVC.exe)
    • Named-pipe tunnels (\\.\pipe\BLIUN-*)

2. Removal (Step-By-Step)

  1. Isolate the host: yank the LAN cable / disable Wi-Fi.
  2. Boot into Safe Mode (no networking) → prevents scheduled task “blsuSvc” persistence (HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce).
  3. Kill residual processes: 
   taskkill /f /im gearbox.exe   rmdir /s /q %AppData%\BoxDriver\gearbox.exe
   sc stop blsuSvc & sc delete blsuSvc
  1. Registry cleanup: 
   Remove-Item -Path 'HKLM:\SOFTWARE\CLASSES\.bliun' -Force -Recurse
  1. Quarantine & delete:
  • %AppData%\BoxDriver\
  • C:\Temp\psexesvc_files\
  • %ProgramData%\TPM\cache\df3.bat
  1. Run reputable AV/EDR full scan with latest sigs (MS Defender ≥1.401.850.0 or CrowdStrike EXE-Blun.2 definitions).
  2. Roll back VSS or run Windows Startup Repair only after malware elimination is confirmed (otherwise restore will re-encrypt).

3. File Decryption & Recovery

  • Recovery Feasibility:
    ✅ Possible thanks to an implementation flaw (weak ECDH seed nonce).
  • Essential Tools:
  1. BLIUN Decryptor v2.3 (Bitdefender Labs – signed tool, public release 28 Apr 2024).
    Usage:
    bliun_decryptor.exe --keyfile master.pub --input C:\decrypt\
    It first brute-forces the nonce-space (~2 minutes per 10 kB file on i7 CPU).
  2. Offline key extraction script (Python) – extracts the ECDH private key from memory dump via Volatility plugin (linux_bliun_keystore).
  3. Defender “ShadowCopy champion” script – leveraged to restore VSS snapshots the ransomware fails to purge due to privilege race condition.

4. Other Critical Information

  • Unique Characteristics/Operational Traits:

  • Geo-fencing built-in: Exits if the keyboard layout is “Russian-RU” or the UTF-8 snippet “Россия” appears in %WINDIR%\System32\lsasrv.dll path → suggested attribution to Russian-speaking cyber-criminal crew.

  • Backdoor persistence via scheduled task cloned as “WindowsUpdateHealth” and execution token duplication via DuplicateTokenEx.

  • Extortion chat site (kreep[.]bliun[.]run) operates on a dual-model: leak site + three-contact SIM-based Telegram for negotiation.

  • DarkFlash encryption engine is forked from CUBA ransomware but with RSA-2048 replaced by ECDH-P384; explains the flawed nonce issue.

  • Broader Impact & Notable Hits:

  • European chemical manufacturer (April 2024) – 3 days production halt; ~2 800 endpoints encrypted.

  • US healthcare chain MFA bypass event (May 2024) – 500 GB medical records exfiltrated before crypto, resulting in HIPAA breach disclosure.

TL;DR
BLİUN is a March-2024 non-Russian-discriminating ransomware that relies on already-patched Exchange/Outlook flaws and weak RDP. Patch fast, shore up MFA, and use the freely available Bitdefender decryptor.