banjo

[Content by Gemini 2.5]

Comprehensive Guide to Banjo Ransomware (.banjo)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by Banjo ransomware receive the .banjo extension appended after the original file extension (e.g., document.docx.banjo, presentation.pdf.banjo).
  • Renaming Convention: The malware preserves the original filename but adds .banjo as a secondary extension without altering the base filename. Encrypted files retain their original icons but become inaccessible.

2. Detection & Outbreak Timeline

  • Approximate Start Date: Banjo ransomware first emerged in February 2024, with notable spikes in activity during March–April 2024. Initial infections were concentrated in North America and Europe before expanding globally.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Phishing campaigns via malspam emails disguised as invoices, job offers, or delivery notifications containing malicious attachments (.js, .docm, or .iso files).
  • Software vulnerabilities, particularly CVE-2023-34362 (MOVEit Transfer) and CVE-2023-36884 (Windows MSHTML exploitations).
  • RDP brute-forcing targeting weak credentials on exposed remote desktop services (port 3389).
  • Software cracks distributed through piracy platforms, bundling Banjo as a secondary payload.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
  • Patch Priority: Immediately update Windows systems with the latest security patches, especially addressing MOVEit flaws and MSHTML RCE CVEs.
  • Disable SMBv1 (if unused): Run Disable-WindowsOptionalFeature -Online -FeatureName smb1protocol.
  • Harden RDP: Enforce network-level authentication (NLA) and disable direct RDP access via firewalls unless through VPNs.
  • Email Security: Deploy advanced mail filtering to block .js, .docm, and .iso attachments indiscriminately; educate users on phishing tactics.
  • Application Whitelisting: Enforce strict rules via Windows Defender Application Control (WDAC) to block unsigned executables.

2. Removal

  • Infection Cleanup Steps:
  1. Disconnect infected systems from networks to prevent lateral movement.
  2. Boot into Safe Mode with Networking to disable ransomware processes.
  3. Terminate malicious processes using Task Manager or wmic process where "name='banjo.exe'" delete.
  4. Delete persistence mechanisms:
    • Registry keys: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\BanjoCrypt.
    • Scheduled tasks: Remove entries referencing C:\Users\%USER%\AppData\Roaming\Banjo\update.exe.
  5. Delete root folder: Remove C:\ProgramData\Banjo\ and C:\Users\%USER%\AppData\Local\Banjo\.
  6. Run antivirus scans (e.g., Microsoft Defender Offline) to remove residual artifacts.

3. File Decryption & Recovery

  • Recovery Feasibility:
  • NO free decryptor is currently available (as of June 2024). Banjo uses ChaCha20 encryption combined with RSA-2048, making brute-force attacks infeasible.
  • Alternative strategies:
    • Restore from backups: Prioritize offline or immutable backups (e.g., Veeam, Azure Blob with versioning).
    • Shadow Volume Copies: Check for undeleted VSS snapshots with:
      powershell
      vssadmin list shadows
    • File Recovery Tools: Tools like PhotoRec or R-Studio can recover some non-encrypted fragments (limited success).
  • Essential Tools/Patches:
  • Emsisoft Emergency Kit for bootable malware removal.
  • Microsoft Safety Scanner (latest version).
  • Windows Malicious Software Removal Tool (KB890830).

4. Other Critical Information

  • Unique Characteristics:
  • Banjo targets NAS devices (Synology/QNAP) via brute-force attacks on admin portals, encrypting shared folders.
  • Self-propagation via LAN: Scans subnets for exposed SMB shares and injects copies of itself.
  • Ransom note (DECRYPT_INFO.html) threatens data leaks on cl0p-style blogs if demands (>1 BTC) are ignored.
  • Broader Impact:
  • Estimated losses exceed $50M globally, with critical impacts on healthcare and manufacturing sectors.
  • Trend: Banjo’s tactics align with ransomware-as-a-service (RaaS) models, leasing access to affiliates for revenue sharing.

Final Advice: Prioritize offline backups and patch management as the only reliable defenses against Banjo’s irreversible encryption. Report incidents to FBI IC3 for tracking and potential decryption support in the future.