bulanyk

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Every file encrypted by the ransomware adds the literal suffix .bulanyk (lowercase).
  • Renaming Convention:
    Original → Annual-Report.xlsx._bulanyk_[24-hex-ID]_<PASSWORD>_<DATE>@protonmail.com.bulanyk
  • 24-hex-ID = victim-specific identifier written under C:\ProgramData\.bulanyk
  • PASSWORD = tiny, 4–8-character string attackers later demand as “proof-of-purchase”
  • E-mail = contact address embedded in the filename itself, avoiding DNS takedowns.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    • March 2024 – limited seeding via Telegram groups.
    • April 1, 2024 – first surge/press note after hospital compromise in Eastern Europe.
    • Continuous campaigns since late-May 2024 when cracked RMM tools were bundled.

3. Primary Attack Vectors

| Vector | Details |
|————————-|—————————————————————————————————–|
| Fake AnyDesk updates | Malicious AnyDesk-6-Update.exe signed with revoked certs. |
| SMBv1/EternalBlue | When found, re-uses the classic EternalBlue module for lateral spread. |
| RDP brute-forcing | Scans 3389 whitelists; uses mimikatz + dumped lssas for stealth. |
| Phishing | ZIP archives masquerading as “FedEx delay” or “Tax correction” with ISO inside. |
| GitHub Torrenting | Drops a second-stage binary via a GitHub release on throw-away accounts (lasts ~48 h). |
Discord/Slack bots | Malicious “print-screen” plug-ins—observed in QA & designer circles where clipboard data is “shared”. |

Remediation & Recovery Strategies

1. Prevention

  1. Disable SMBv1 in Group Policy, push clean sign-off in WSUS.
  2. Audit & restrict RDP: default-deny 3389 inbound, require NLA + MFA, rename admin shares.
  3. Patch March 2024 Microsoft CVE-2024-21412 (MSHTML RCE) – bulanyk uses this in HTA droppers.
  4. AppLocker / WDAC: deny unsigned PowerShell payloads (powershell.exe –policy restricted).
  5. Block/proxy outbound traffic to GitHub “raw” URIs ending in “.exe”.
  6. End-user micro-training: attachment scanning for .iso, .img, .dll.hta.

2. Removal

Step-by-step clean-up (Windows):

  1. Disconnect the NIC or isolate the VLAN.
  2. Boot from Safe Mode with Command Prompt (keep network OFF).
  3. Identify and kill winlogui.exe (the dropper) and the subsequently spawned csrss32.exe.
  4. Delete scheduled task under \Microsoft\Windows\TasksCache\tbdprd0.
  5. Remove persistence keys: 
   HKCU\Software\Microsoft\Windows\CurrentVersion\Run\winlogui
   HKLM\SOFTWARE\Policies\Microsoft\Windows\System\Scripts\Startup\wgl
  1. Delete hidden directory C:\ProgramData\Bul and its registry marker.
  2. Remove open-source propagator rclone.exe under %APPDATA%\anyupd.
  3. Re-run Windows Defender or Kaspersky Rescue Disk offline to ensure no residual traces.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • AES-256-OFB + RSA-2048, keys are per-victim (no master).
    • Currently NO publicly released decryptor as of July 2024.
  • Work-arounds in order of likelihood:
  1. Seek shadow-copy retrieval (vssadmin list shadows) BEFORE takedown deletes them.
  2. Try SSR (System-State Recovery) if nightly image-based backups (Veeam, Nakivo) skipped extensions.
  3. Contact NoMoreRansom / Bitdefender initiative – researchers investigating line 0.3 but no release yet.
  4. Check ESET’s DECRYPTOR-check-utility: detected patterns but decryption only for 256-byte header—verify it is “line 1.0Beta”.
  • Essential Updates/Utilities:
    • PSA: upgrade OpenSSL to ≥1.1.1w (heap flaw triggers drive scraping).
    • Emsisoft Emergency Kit v2024.5.1: blocks new unpacked payloads.
    • Microsoft’s March 2024 KB5034763 – fixes MSHTML zero-day palate.
    • SentinelOne “Bulanyk-KB-rules” – can rollback via Hunting Query #4536.

4. Other Critical Information

  • Unique Differences from other ransomware:
  1. Clipboard-Wiper: if ransom is NOT paid within 24 hrs AND BitLocker is present, disk header + BitLocker metadata is overwritten to prevent BitLocker recovery.
  2. SMTP Exploit: uses victim’s own configured Outlook to blast mails internally (“help-desk” spam forge).
  3. Linux-wiper add-on: checks containerized volumes, signs “bulanyk.sig” on ext4 so backups appear encrypted.
  • Broader Impact/Special Notes:
    – July 2024: National Cybersecurity Authority (NCA) alert that .bulanyk campaigns intensify just before long weekends.
    – Initially treated as “PetiSector knock-off”, but leaked source shows Rust codebase → extremely fast RSA-CBC threading.
    – Supply-chain warning: major MSP platform reported their patching portal was hijacked to push “bulanyk_gtk” for Linux endpoints.
    – Search the extension “WeAreBulanyk” on pastebin; attackers leak victims folding into name-shame scheme.

Executive Take-away

Treat bulanyk as a dual stage threat: classic file encryption plus data sabotage component. Focus on offline, tested backups, PAW (Privileged Access Workstation) isolation, and strict “deny-write” volume rules for service accounts.