bagi

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends “.bagi” as a secondary extension to every encrypted file. The original file name remains intact—only the new suffix is added.
  • Renaming Convention:
    <original_name>.<original_extension>.bagi
    Example: Document.docx becomes Document.docx.bagi.
    A plaintext ransom note (_readme.txt or readme.txt) is dropped into each folder alongside encrypted files.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The “.bagi” variant of STOP/DJVU ransomware began circulating in late-June 2019. It quickly became one of the most active families throughout the second half of 2019 and continues to resurge periodically, primarily via cracked software and adware bundles.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Pirated software & keygens – Masquerades as activators for Adobe, Microsoft Office, video editors, games, etc.
  2. Malvertising & fake update pages – Victims are redirected to bogus Flash/Chrome update sites.
  3. Spam email attachments – Compressed archives (.zip, .rar) containing disguised JavaScript files; subject lines like “Invoice-12345.zip”.
  4. Keygen cracks – Torrents labeled “full premium version” that execute an NSIS installer dropping the payload.
  5. Trojanized browser extensions – Some Chrome/Edge add-ons silently fetch the ransomware dropper.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable SMBv1 (Stop-WinService smb1) and patch EternalBlue (MS17-010).
    • Block outbound connections to C2 servers at the firewall (e.g., 185.238.139.208/24).
    • Train users never to run cracks or open dubious email attachments.
    • Maintain 3-2-1 backups (3 copies, 2 media, 1 off-site/off-line).
    • Enable Windows Defender ASR rules: Block executable content from email client & webmail.
    • Restrict local admin rights; use LAPS for unique local admin passwords.
    • Patch Adobe Flash/Java/RDP (enable NLA & limit RDP to VPN).

2. Removal

  • Infection Cleanup (step-by-step):
  1. Interrupt network & Wi-Fi immediately to stop spread to mapped drives and drop re-encryption.
  2. Boot into Safe Mode with Networking.
  3. Install & update Malwarebytes, Sophos HitmanPro, or Trend Micro Ransomware File Decryptor. Run a full scan to quarantine bagi loaders, task-schedule persistence, and rogue registry keys (HKCU\Software*BAGI*, HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run).
  4. Delete shadow-copies remnant scripts and clean up Scheduled Tasks via schtasks.exe /delete /tn random.
  5. Change all local and cached domain passwords; verify no lateral move occurred.
  6. Suspend re-imaging and restore only after confirming complete eradication (check %AppData%\Local\bagi***.exe or random-named executables).

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Online IDs (generated with remote server contact): No free decryptor.
    • Offline IDs (code-present “t1” after personal ID): Decryption is possible using Emsisoft Stop/Djvu Decryptor v1.0.0.5+ if a matching offline key is in the tool’s key list.
    • Always run sysinternals ProcMon in parallel to guarantee no lingering executables; the decryptor will not run if active malware is present.

  • Essential Tools / Patches:
    – Emsisoft Stop/Djvu Decryptor: Download & follow “README decryption.txt”.
    – WiseGEEK Ransomware ID Tool for victim confirmation.
    – Emergency Patch Rollup (Windows 7 ESU + cumulative Windows 10) to close SMB/RDP avenues.
    – Kaspersky Anti-Ransomware Tool (KART) for sub-OS boot remediation via Kaspersky Rescue Disk.

4. Other Critical Information

  • Unique Characteristics:
    • Generates a unique 40-byte online key (<PCNAME>-77xREEkKpersonalID.bagi note) which precludes brute-force.
    • Backups prior to infection cannot be accessed by file-crypt; yet the background loader deletes shadow copies (vssadmin delete shadows /all) and lastly adds Windows Defender exclusions so it can stay latent.
    • Persist via task-scheduler “Windows Application Mobility Checker” plus registry Run keys under random GUID names.

  • Broader Impact:
    • Over 600,000 victims have been logged by ID trackers since 2019 (Source: Emsisoft telemetry).
    • The family is known to drop additional infostealers (RedLine, Vidar) following encryption, turning an incident into a double-whammy data-breach.
    • Countries with weak software-piracy enforcement (Russia, Brazil, India) show the highest prevalence, but Western English-speaking regions see spikes whenever new Adobe crack bundles circulate.

Bottom line: Treat bagi like every STOP/Djvu derivative. Eradicate completely, restore from clean backups where decryption fails, and rigorously block the pirated-software vector to stop repeated nightmares.