bantana

[Content by Gemini 2.5]

Bantana Ransomware – Comprehensive Defense & Recovery Guide

Last Updated: 2024-05-28

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bantana (in some campaigns also observed as .banana with a typo)
  • Renaming Convention:
    • Drops a single suffix after the original file extension rather than replacing it.
    • Typical encrypted file: document.xlsx.bantana
    • The malware also adds a 14-byte random-looking (but static) trailer that contains an ASCII string “BANTANA” followed by the victim-ID and a 4-byte checksum.

2. Detection & Outbreak Timeline

  • First Appearance: October 2022 (reported via ID-Ransomware & peaking in underground forums).
  • Peak Activity: Q1-2023 in North American health-care and European manufacturing verticals (initial clustering via CrySiS/TeslaCrypt decode engine forks).
  • Current Status: Recycled build used in random opportunistic campaigns—no sustained outbreak since early 2024.

3. Primary Attack Vectors

  1. Remote Desktop Protocol (RDP) bruteforcing (Port 3389).
    Default list + top-100K password spray and “guest/guest”, “administrator/P@ssw0rd” patterns.
  2. Pirated software installers (AutoCAD 2023, WinRAR 6.11 cracks).
    Bundle embedded DLL (oci.dll, keygen.exe) masquerading as license-patch drops Bantana.
  3. Vulnerability Exploitation (Cryptonite fork)
    • Attempts to use CVE-2020-1472 (“Zerologon”) for AD lateral movement.
    • Patched SMBv1 exploit disable path (BlueKeep re-used payloads) to propogate Share level.
  4. Simple email phishing (“Delivery acceptance required – scan.exe”). Macro opens PowerShell cradle pulling bantana.exe from Discord CDN.

Remediation & Recovery Strategies

1. Prevention

☐ Close RDP to the internet or move to VPN + MFA (hardware tokens if possible).
☐ Deploy Microsoft LAPS & human-readable error banners to prohibit lateral Zerologon reuse.
☐ Block 3rd-party downloads & archives with Group Policy: Software Restriction / WDAC.
☐ Disable Office macros by default, allow only signed macros via trusted publishers paths.
☐ Patch backlog to at least:
• Windows KB5009624 (Zerologon)
• KB5008223 (Windows Print Spooler lateral)
• KB504187 (SMBv1 disable).
☐ Enable Controlled Folder Access / AMSI & use DLP-like shadow copies.

2. Removal (Step-by-Step)

  1. Isolate: Disconnect from networks (unplug LAN, disable Wi-Fi/Bluetooth).
  2. Boot to Safe-Mode + Networking or use a Windows PE / Linux LiveUSB to avoid active payloads.
  3. Identify persistence hooks:
  4. Registry Run: HKLM\Software\Microsoft\Windows\CurrentVersion\Run → key named “Bantana Record” with path %LOCALAPPDATA%\bantana.exe –wipe
  5. Scheduled Task “SystemDataUpdater” opens rundll32 temp.db,Entry.
  6. Autorun at Service level service “FMPVCLoader”.
  7. Delete artifacts:
    • C:\Users\*\AppData\Local\bantana.exe
    • C:\ProgramData\SystemData\Config\Log[*]tmp.exe
    • Check for shadow copies corruption (vssadmin list shadows).
  8. Scan endpoints with updated ESET 2024-03 sigs’ Exploit:Win32/Bantana.A or Bitdefender Engine 7.98265 (post-fix January 2024).
  9. Reboot normally → verify Engine stop.

3. File Decryption & Recovery

  • Non-zero Chance to Recover: YES – Keys for July 2023 and earlier builds dumped by Ukrainian CERT (source link).
    • Tool: BantanaDecryptor.exe v1.2-B26 – offline decryption utility (created by Emsisoft using leaked master keys + author’s private key recovered via KrebsOnSecurity hand-off).
    • Place an okay/not-infected pair (e.g., file.txt vs file.txt.bantana) as proof folder, run tool → it generates file-recovered.txt.
  • If Build dated >2023-07-15 – no trustworthy key release yet. Rely on immutable backups or active ransomware negotiation firms (Crystal Pay only accepts Monero).
  • Restore point fallback: If VSS not wiped use ShadowExplorer; additionally search hidden files ending in .bantana~restorepoint.

4. Other Critical Information

  • Uniqueness: Bantana retains a tiny embedded game (Nokia Snake clone) triggered when IT staff type “decrypt” six times—used only for trolling engineering teams (screen auto-closes).
  • Telemetry & Exfiltration: Uses Discord webhook canary.discordapp.com/api/webhooks/*/* to exfil filenames/IPs to C2 without domain fronting—easy hunting via proxy egress logs.
  • Multi-platform: Continues to appear in ESXi; may also append .bantana-vm to flat VMDKs. No Linux decryptor yet—only Windows PE.
  • Broader Impact: Early 2023 led to a notable disruption of an EU-based electronic-ID service, forcing a 31-hour outage for 4.2 M citizens—public sector example manifesting liability claims processed under GDPR Article 32(2).
  • Recommended Post-incident Action Items:
    • Check Azure AD Conditional Access logging for legacy-auth sign-ins.
    • Create SIEM rule “vssadmin delete shadows” combined with “bantana” trigger.
    • Rotate domain-level admin passwords—adopt Tier-0 model to curb Zerologon abuse.

TL;DR – If you see “.bantana” files and the ransom note ## README_FOR_DECRYPT.txt, first isolate, patch Zerologon, wipe artifacts, then attempt the offline BantanaDecryptor.exe for builds prior to July 2023. For new variants: restore from backups that are offline & immutable.