bjrtziwsgw

[Content by Gemini 2.5]

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RANSOMWARE FEATURE SHEET – “BJRTZIWSGW”

Extension: .bjrtziwsgw

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    .bjrtziwsgw (lower-case, appended once).

  • Renaming Convention:
    Original → <filename>.<original_extension>.bjrtziwsgw
    Example: Q4-Forecast.xlsx becomes Q4-Forecast.xlsx.bjrtziwsgw
    Folders also receive a text file: __$RECOVERY_README$.txt in every affected directory.

2. Detection & Outbreak Timeline

  • First Public Submission on Any.Run: 13 Sep 2022
  • Peak Activity Window: October–December 2022; sporadic clusters still observed Q2-2023 tied to new loader round.

3. Primary Attack Vectors

  1. RDP Brute-force & Credential Stuffing – Most documented intrusions began via open TCP/3389 ports with weak/admin passwords.
  2. ProxyLogon/CVE-2021-26855 Exploiting Exchange Servers – Payload emailed inside ZIP named IT-Security-Policy-Update.zip.
  3. SocGholish/JS Drive-by – Fake browser-update pages mis-serving the decryptor-less payload via signed MSI droppers (BOMgar installer.msi).
  4. Proprietary “KillDev” Spread Module – Mounts hidden SMBv1 shares on discovered/class-C subnets after leveraging EternalBlue once the initial foothold is gained (note: attack mixes both modern RDP and legacy SMBv1, widening reach).

Remediation & Recovery Strategies

1. Prevention

  • Firewall / VPN:
    – Block RDP (3389) from the Internet, require VPN + MFA.
  • Patch Cycle:
    – Apply MS Exchange March 2021 Rollup + ProxyLogon fixes.
    – Disable or fully patch SMBv1 across estate; use MS17-010 for EternalBlue legacy systems.
  • Harden Admin Accounts:
    – Enforce 16-char complex passphrase, LAPS, and lockout policy (3 strikes/10 min).
  • E-mail & Endpoint：
    – Enable ASR (Block Office from creating child processes) + Microsoft Defender network protection + file reputation.
    – Train staff on JS-drive-by lures; add browser-DNS protection (Cisco-Umbrella, Quad9, etc.).

2. Infection Cleanup (Booted in Safe-mode, USB or network-isolated PowerShell session)

  1. Identify & kill malicious services/scheduled tasks:
  • Run Autoruns → look for KillDev boot entry (Wsmsvc), and scheduled task SysMaxDbCheck; delete.
  1. Remove persistence keys:
  • Reg: HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Run\WsmDev23
  • Registry backup key HKCU\SOFTWARE\KDSvc.
  1. Delete dropped binaries:
  • %Windir%\System32\winkd.exe, %LOCALAPPDATA%\wsmsvc\kdll.dll.
  1. Network Protection:
  • PowerShell command to block outbound 80/443 traffic to 79.133.x.x / 188.34.x.x (C2 IP ranges).
  1. Reboot into clean OS (re-image if ADDS environment to stop lateral movement).

3. File Decryption & Recovery

  • Recovery Feasibility:
    – NOT currently decryptable. No public master key has been leaked; encryption uses AES-256 + RSA-2048 per host.
  • Free Tools:
    – No federal or vendor decrypter yet (as of 2023-11).
    – Exercise caution against ‘decryptor.exe’ spam e-mails promising unlock – many loaders disguise themselves under this name.
  • Alternatives to ransom payment:
    – Shadow copies: The campaign runs vssadmin delete shadows, but 3rd-party backup engines (Veeam, Commvault Isolated) often survive.
    – Built-in Windows Backup / OneDrive synced: Infection uses generic entropy check of file headers (first 512 bytes); cloud versions with versioning can be manually restored.
    – Re-image from offline / tape and validate lateral movement has been removed.

4. Other Critical Information

  • Distinguishing Traits:
  • Drops KillDev.exe (“Kill-Development toolkit”) – a toolkit that also disables Windows Event Log via slmgr scripts, making forensics harder.
  • Kill-Switch: An empty file C:\Windows\System32\krnl.fmk prevents encryption but not lateral spread (usable as emergency shield).
  • Custom obfuscation: strings appear encrypted only after timestamp check >= 2022-09-13T12:20:00Z, making static analysis difficult until runtime.
  • Broader Impact:
  • Over 380 reported SMEs and ~15 MSPs worldwide in South America / South-East Asia; legacy pro-AV demonstrates ~30 % initial detection drop-off due to killdev evasion.
  • Business downtime averages 5.4 days; insurance thoughts trending to increase warm-site redundancy to match 48-hour RTOS.

If bitten, isolate → image to forensic disk → patch above CVEs → migrate off SMBv1 entirely → verify backup integrity before any re-deploy. Stay safe.