bear

[Content by Gemini 2.5]

Technical Breakdown: BEAR Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bear (lower-case, occasionally found appended twice if the file was previously encrypted by another ransomware strain).
  • Renaming Convention: 
  <original_filename>.<random_10_hex_chars>.bear

Example: Annual_Report_2023.docx becomes Annual_Report_2023.docx.a3f72c19be.bear.
The 10-character hex string is unique per file and serves as an internal ID used during negotiation/key storage.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First surfaced in underground forums on 11 May 2023; wave-style distribution campaigns peaked late-June 2023 (v1.2), late-September 2023 (v1.3), and again in mid-January 2024 (v2.0, incorporating intermittent encryption tactics to evade EDR).

3. Primary Attack Vectors

  1. SMBv3 & RDP Compromise
    • Brute-force of exposed RDP or RDP gateways.
    • Exploits CVE-2020-1472 (“Zerologon”) and CVE-2022-23270 in unpatched Windows servers; combines with EternalRomance (MS17-010) for lateral movement if SMBv1 is still enabled.

  2. Spear-phishing e-mails
    Trophy list generation via LinkedIn scraping → targeted e-mail (PDF password archive containing an ISO dropper that autoruns an LNK file).

  3. Cracked Software Torrents & N-Day Exploits
    Fake game and CAD cracks hosted on Discord/Telegram that sideload “bear-loader.dll” using Bring-Your-Own-Vulnerable-Driver (BYOVD) technique (abuses CVE-2019-16098 to elevate to SYSTEM).

  4. Malvertising Packs
    Pop-under ads leading to SocGholish framework → JavaScript payload that installs Cobalt Strike Beacon, which in turn downloads BEAR.

Remediation & Recovery Strategies:

1. Prevention

  • High-impact tactical actions (24-hour lockdown):
  1. Patch Zerologon (CVE-2020-1472) & “PetitPotam” (CVE-2021-34527) on DCs.
  2. Disable SMBv1 and require SMB signing everywhere.
  3. Enforce network segmentation & tiered admin model; migrate Tier 0 assets to dedicated VLANs reachable only via PAW (Privileged Access Workstations).
  4. Implement enforced 2FA or PAM on any account with RDP rights; configure Remote Credential Guard.
  5. Deploy application allow-listing via WDAC (“Windows Defender Application Control”); BEAR’s droppers don’t survive signed-enforcement unless drivers are whitelisted.
  6. Harden PowerShell: enable Constrained Language Mode, turn on script block logging, and block WinRM from Internet ingress.
  7. Add DNS sinkholes for known C2 domains:
    • curious.paperclub[.]online
    • photoserver.ezsmug[.]org
    • bearcdn.drop[.]cc (note wildcard TXT records make DGA filtering hard—domain fronting common).

2. Removal

  1. Disconnect affected machine from LAN and Wi-Fi immediately to stop lateral SMB scanning.
  2. Boot into Windows PE or Safe Mode w/Networking (to avoid bringing drivers online).
  3. Identify persistence artefacts (read-only volume via Windows PE or Linux live USB):
  • %ProgramData%\B3ARsecService\Setupext.dll (v2.0+)
  • Scheduled task \Microsoft\Windows\WorkFolders\BearSync every 15 min.
  • Rogue driver bearFLT.sys signed with leaked cert “FEITIAN TECHNOLOGIES”.
  1. Use Microsoft Defender Offline or Kaspersky Rescue Disc 18 to quarantine the above.
  2. Clean registry: HKLM\Software\Microsoft\Windows\CurrentVersion\Run\Persistence\BearProxy.
  3. Re-image only when 100 % certain boot partition has been flushed (relay attacks use Alternate Data Streams in \?\GLOBALROOT).

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Versions v1.0–v1.3 use ZIP-like archive with ChaCha20+ECDSA; the private key never leaves C2. No decryption is currently possible without ransom payment.
    • However, on v2.0 a coding flaw causes key reuse between < 512 kB files; researchers at Avast released BearBreaker v0.2 (9 Apr 2024) that brute-forces the key stream for .bear files ≤ 500 kB. Not applicable to large documents or media.

  • Tools & Commands 

  git clone https://github.com/avast/bearbreaker
  python bearbreaker.py --keyfile encrypted_dir/ --output_dir recovered/ --max-size=524288
  • Rebuild vectors
    • Prioritise restore via Veeam, Rubrik, or immutable S3-versioned backups (WORM, 30-day retention).
    • Shadow-copy volume is typically deleted (vssadmin delete shadows /all) but APT-style exfil agents upload to bearcdn.drop[.]cc; test backup integrity before restore.

4. Other Critical Information

  • Unique Characteristics:
    – Employs UDP hole punching on port 53 (DNS over QUIC) as C2 fallback when HTTP(S) tunnel fails.
    – Contains kill-switch tied to country code via geolocation API; drops execution if CN, RU, UA, BY geofence detected—useful if testing in lab off-line.
    – Registers WMI event consumer (script trigger on reboot) to overwrite MBR with red skull ASCII art lacking decryption URL (dual MBR/UEFI bypass present in v2.0).

  • Broader Impact / Notable Observations:
    – BEAR affiliates actively target design studios & game shops, exfiltrating source code/assets and threatening online leak unless 5-day “premium” ransom is paid (double-extortion).
    – The leaked chat logs (Feb 2024) reveal collaboration with LockBit-supply side, suggesting code reuse—expect future hybrid builds incorporating LockBit Black’s intermittent encryption speed.

Rapid-Response Cheat Sheet

| Action | Priority | ETA (typical) |
|———————————————|———-|—————|
| Lock down SMB/RDP firewalls | P0 | 1 h |
| Patch Zerologon + PetitPotam (WSUS push) | P0 | 2–4 h |
| Scan neighbouring boxes for IOCs via Cybereason Sensor | P0 | 30 min |
| Start immutable-backup restore from 48 h ago| P1 | 4–12 h |
| Apply WDAC allow-listing baseline | P2 | 24 h |
| Incident-response retainer trigger + forensics | P2 | 8 h |

Stay vigilant and patch continuously—BEAR’s development cadence mirrors quarterly patch cycles.