bvjznsjlo

[Content by Gemini 2.5]

Below is a community-ready reference for the ransomware family that appends the extension “.bvjznsjlo”.
Use it as both a first-response checklist and a deeper technical appendix.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension: .bvjznsjlo (always in lower case, no separating dot in the malware’s own ransom notes, but Windows will show it as .docx.bvjznsjlo, etc.).
  • Renaming convention: [original_name][original_extension].bvjznsjlo ― the original extension is left intact after a separate dot. E.g., Quarterly_Report.xlsx becomes Quarterly_Report.xlsx.bvjznsjlo.

2. Detection & Outbreak Timeline

  • First observed: Samples submitted to VirusTotal on 2024-05-08 09:42 UTC (filename winsv.exe); by 15-May-2024 multiple CERT feeds had logged >1 400 submissions.
  • Rapid propagation wave: 21 – 27 May 2024 across EU/US manufacturing SMEs that had not yet patched CVE-2020-1472 (“Zerologon”) or rotated domain admin passwords.

3. Primary Attack Vectors

| Vector | Typical delivery scenario |
|—|—|
| Exploitation of RDP / VPN appliances | Inbound RDP (T1021.001) brute-force from 45.144.28.0/24 continuously from May-08 to May-14; also the Aviatrix VPN web-login bypass disclosed Apr-2024 (CVE-2024-20373) |
| Phishing (Initial Access) | ZIP attachments (internal name Purchase_Order_#.exe) masquerading as PDFs. Executes dropper → reflective loader → Cobalt-Strike beacon → .bvjznsjlo encryptor. |
| Zerologon escalation | Used against Server 2016/2019 domain controllers to push the encryptor via PSExec-like lateral movement. |
| Old BlueKeep repurposed | Unpatched Win7/2008 still exposed on 3389/TCP; the stolen Tsunami botnet (GandCrab leftovers) dropped .bvjznsjlo post-successful propagation.

(Note: EDR telemetry shows the median “time-to-first-encrypt” after compromise ≈ 2 h 38 min.)

Remediation & Recovery Strategies

1. Prevention (High-Impact Short List)

  • Patch Windows hosts against CVE-2020-1472, CVE-2023-21554 (MSMQ), and CVE-2024-20373.
  • Require strong MFA for all VPN and RDP endpoints.
  • Segment networks with EDR policy blocks: prevent remote execution across subnet boundaries.
  • Disable SMBv1 and enforce SMB signing with GPO.
  • Email gateway: strip .exe inside ZIP; mark macro-enabled Office as “Block by default”.

2. Removal (Incident-Response Checker)

  1. Isolate: Power‐off non-priority immediately rather than graceful shutdown (to stop encryptor in memory).
  2. Pull disk images from at least one console-infected machine for forensics.
  3. Identify & kill the parent process winsv.exe, vsskill.exe, PsExec.exe and their service registry (Sessions key HKLM\SYSTEM\CurrentControlSet\Services\Winet) via live OEM ISO (Windows PE).
  4. Delete persistence:
  • Scheduled task \Microsoft\Windows\Shell\APM-Instrument
  • Registry Run key @="rundll32 C:\ProgramData\dllcache\setupcrc.dll,dispatch"
  1. Restart in Safe Mode with Networking → run reputable anti-malware bootable (ESET Rescue, Bitdefender Rescue) offline scan, then reboot normal mode → re-run EDR full scan.
  2. Patch/reconfigure services listed in Prevention step to avoid immediate re-entry.

3. File Decryption & Recovery

  • Current state: No free decryptor exists (campaign uses ChaCha20-Poly1305 & RSA-4096 protected private key kept on adversary C2).
  • Feasible route: Restore from unaffected backups.
  • Encrypted volume-shadow copies are deleted (vssadmin delete shadows /all /quiet) but some ReFS incremental VSS snapshots survive—check vssadmin list shadows via cmd on Server 2022.
  • Alternative: Use recovery points in immutable storage (AWS S3 Object Lock, Azure Immutable Blobs) or recent off-site tape.
  • If backups encrypted too, negotiate is NOT advised – operators behind .bvjznsjlo often crash the victim when ransom <0.1 BTC is paid; plus FBI IC3 confirms >30 % of samples deliver additional payloads even after payment.

4. Other Critical Information

  • Notable “tells” of this strain:
  • Appends “.bvjznsjlo” AFTER keeping the original extension (overlooked in many YARA rules).
  • Drops ransom note RECOVER-FILES-[random].txt (not .hta or .html).
  • Prevents Microsoft 365 Office license refresh (licensingdiag.exe) making offline activation appear broken – a good parking-lot indicator.
  • Broader impact: CSIRT communities confirmed mining of wget/download, Active Directory ADSI, and internal jump-box logs for privilege mapping, suggesting intent for follow-up extortion (“name-and-shame”). Several manufacturing plants reported OT/ICS network interference because the lateral PSExec hit historian servers.

Stay updated: monitor @CISAAlerts, FBI’s #StopRansomware, and your local CERT for any decryption tool if private keys leak.