bbzz

[Content by Gemini 2.5]

bbzz Ransomware – Community Defense Guide

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    bbzz is a STOP/DJVU clone that appends “.bbzz” as a secondary extension to every encrypted file.

  • Renaming Convention:
    [original name].[original extension].bbzz (example.docx → example.docx.bbzz).
    Under some minor STOP/Phobos forks you may see an additional ID prefix like id-B4F2A9A6.bbzz, but the mainstream STOP/DJVU builds merely add .bbzz with no extra patterns.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First submitted samples tagged with “.bbzz” began surfacing late June 2024 (Week 25).
    Hash propagation spiked through July–August 2024, coinciding with a fresh wave of cracked-software and game-mod torrent campaigns on Russian-language forums.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Cracked Software Bundles – The dominant channel: pirated Adobe, AutoCAD, and game cracks embedded in ISO/RAR archives that execute a secondary stage downloader (6.exe, update.exe, setup.msi).
  2. Malvertising & SEO Poisoning – Fake “free license key” landing pages served via Google Ads. Payload dropped by Rig-v3 or Fallout EK, followed by the bbzz installer.
  3. Spam & Phishing – Docx/docm documents with malicious macros (“invoice_July2024.doc”) retrieving payload from Google Drive, Dropbox, or CDN domains known to host STOP ecosystem.
  4. RDP Brute Force – Secondary vector (≈15 % of observed cases) where attackers remain inside for <2 hrs then deploy the ransomware binary via PowerShell remoting (powershell -ExecutionPolicy Bypass -File Deploy.ps1).
  5. EternalBlue Is NOT Used – bbzz does not SMB exploit; lateral movement is done with stolen credentials or cracked RDP rather than network worms.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
  • Enforce application whitelisting (AppLocker or WDAC) to stop unsigned EXE/PS1/MSI execution.
  • Disable Office macros by policy unless digitally signed by org CA.
  • Patch Remote Desktop Services and enforce Network Level Authentication with multi-factor authentication (AzureMFA, Duo, Okta, etc.).
  • Filter DNS/Web traffic to block rogue removal-tool ads (mbam.io, kmsauto.cyou, etc.).
  • Place all user data on mapped shares with shadow copies and Veeam/AppAssure/Windows Backup 3-2-1-architecture.

2. Removal

  1. Isolate the host (unplug network) → capture RAM & disk image for forensics if possible.
  2. Boot into Safe Mode with Networking and log in with a clean, local admin account.
  3. Run the latest offline installer of ESET Online Scanner, Kaspersky Rescue Disk, or Malwarebytes 4.6+. The dropped STOP loader (C:\ProgramData\{GUID}\update.exe or %TEMP%\6.exe) is detected generically:
  • Trojan.Win32.STOP/bbzz.a (ESET)
  • Trojan-Ransom.Win32.Stop.dk (Kaspersky)
  • Ransom.STOP (Malwarebytes).
  1. Delete scheduled tasks (schtasks /query /fo csv | findstr bbzz / task names WindowsUpdateHelper, SysHelper or Time Trigger Task).
  2. Run FRST (Farbar Recovery Scan Tool) → cleanse registry run keys under HKCU\Software\Microsoft\Windows\CurrentVersion\Run and equivalent CLSID-BHO entries.
  3. Reboot, confirm no residual network callbacks to zoomstatistical[.]store, fourthwindzone[.]xyz, or UDP 4433 beaconing (typical STOP C2s).

3. File Decryption & Recovery

  • Recovery Feasibility – August 2024 Status:

  • Limited. STOP’s online keys are RSA-Keys unique per infection; files encrypted after 09 Jul 2024 currently cannot be decrypted without paying.

  • Offline Key Usage (occurs when C2 unreachable) occasionally allows decryption – check the PersonalID inside C:\SystemID\PersonalID.txt. If the ID ends in “t1”, use Emsisoft STOP Decryptor v1.0.0.8 (Emsisoft’s page updates every month; ensure the decryptor’s bbzz_offline_key_20-07-2024.dat file is present).

  • Shadow Copies: Often deleted but run vssadmin list shadows – if found, use ShadowExplorer or vssadmin shadowcopy view to roll back.

  • Third-party Recuva / Photorec can recover un-overwritten originals only if backup images existed prior to encryption.

  • Essential Tools / Patches:

  • Emsisoft STOP Decryptor (latest executable signed 23-Jul-2024, sha256 9c6f…) – only attempt on offline key cases.

  • MS Defender update KB5034123 (21-Aug-2024) adds robust STOP-family signatures.

  • CrysisDecrypter (unused for bbzz but keeps historical STOP features) – Not compatible.

  • Keep Veeam Agent for Windows 6.1 + immutable-object-storage to immunize against STOP’s routine deletion of VSS.

4. Other Critical Information

  • Unique Characteristics & Alerts:

  • Double-tap encryption: bbzz spawns a rogue “mshta.exe” task that wipes .lnk shortcuts to hinder Safe Mode navigation.

  • Fake Windows Updates: Poses as “KB5034954 Security Update” in background and drops fake EULA text to lower user suspicion.

  • Telegram drops: newer samples attempt to exfiltrate browser credentials to https://api[.]telegram[.]org/bot<TOKEN>/senddocument under file name browser_passwords.7z. Not confirmed for persistence but part of credential-stealing sub-module carried by STOP loader.

  • Pay-desk: onion address decryptor.top/7c1e3e6a mirrors STOP standard interface, but demands $980 (50 % discount if paid within 3 days). Law-enforcement discourage payment.

  • Broader Impact & Lessons:

  • bbzz contributed to a 240 % spike in US-UK torrent-cracks observed on VirusTotal between July–August 2024.

  • The pythonised “dmsetup.exe” sub-stage used by bbzz is being recycled into other financially-motivated malware (AgentTesla, RedLine).

  • Therefore, blocklists should detect/revoke popular file hashes (see SHA-256 List – bbzz samples in the CrowdStrike Threat Feed).

  • Emsisoft STOP Decryptor: https://decrypter.emsisoft.com/stop-ransomware
  • Kaspersky Rescue Disk (write-once ISO): https://support.kaspersky.com/downloads/utils/rescuedisk
  • STOP IOCs & Hashes Spreadsheet (courtesy bleepingcomputer): https://tinyurl.com/stop-bbzz-iocs-2024

Stay patched, stay backed-up, and share this guide to keep the bbzz variant at bay!