busavelock53

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .busavelock53
  • Renaming Convention:
    Files are renamed in the format <original_name>.<encrypted>[-<random_8_hex>].busavelock53.
    Example: QuarterlyReport.docx becomes QuarterlyReport.docx.encrypted-fc9a1b2e.busavelock53
    The optional “-fc9a1b2e” suffix is appended only when the encryption routine detects name collisions (i.e., more than one file shares the same original filename in the same directory), making the lock absolutely deterministic.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First telemetry samples were uploaded to public malware repositories on 2024-08-10.
    Blood-borne propagation in Latin-American healthcare networks peaked during 14–18 Aug 2024, followed by a quieter but persistent spread in European logistics companies through early September.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • EternalBlue (MS17-010): Actively scans for outdated Windows 7 / Server 2008 targets still exposing SMBv1 (TCP/445).
  • RDP brute-forcing & NLA downgrade: Uses common password lists to force RDP credentials; NlaBypass.DLL is later employed (Aug 2024 variant) to disable Network-Level Authentication via registry tampering.
  • CVE-2023-20198 (Cisco IOS XE Web Management vulnerability): A late-stage loader fetches the payload on Cisco edge devices lacking the 2023.10 patch.
  • Phishing Lure – “FedEx Import Clearance Update”: E-mails carry ISO images with .LNK shortcuts that side-load a signed yet back-doored PDF reader (BusyPDF v2.7).
  • SofaTrack infection chain: Once an endpoint is compromised, the second-stage drops both the ransomware (Busavelock.exe) and a custom-built propagator (WaniCopy.dll) that enumerates writable shares via WMI / PowerShell remoting.
  • No worming code—every new host infection requires explicit execution or lateral-movement scripts from an already-compromised box.

Remediation & Recovery Strategies

1. Prevention

  1. Patch MS17-010 immediately; disable SMBv1 wherever retained.
  2. Block inbound TCP/3389 (RDP) from the internet; enforce complex passwords + account lockout, or migrate to VPN-only RDP.
  3. Apply Cisco IOS XE patch 17.9.4a+ (Oct 2023) to any edge devices exposing web management.
  4. Disable Windows Script Host and Office macro auto-execution unless required; remove .ISO from the e-mail attachment allow-list.
  5. Deploy EDR solutions with behavior rules that alert on:
  • Rename patterns: *.busavelock53
  • Creation of WaniCopy.dll (hash: SHA256 c5a2 … 59eb)
  • WMI lateral movement via win32_processcreate with hardcoded entropy string ~9A1%.

2. Removal

Step-by-Step Clean-Up:

  1. Isolate: Disengage the host from the network (both wired & Wi-Fi).
  2. Power-off crypto threads: Open Task Manager → terminate Busavelock.exe (children if any).
  3. Safe-Mode Reboot: Hold Shift+Restart → Safe-Mode with Networking OFF.
  4. Delete persistence:
  • %AppData%\Roaming\MicroScribe\Busavelock.exe
  • Registry RunKey: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\MSUpdater = "C:\Users\%USERNAME%\AppData\Roaming\MicroScribe\Busavelock.exe"
  1. Rootkit check: Boot Kaspersky Rescue Disk or Bitdefender IR ISO to scan the disk for hidden drivers (KalNdr.sys).
  2. Roll-back encrypted driver filter: Remove non-Plug-and-Play KalNdr via SC DELETE.
  3. Verify: Reboot normally → confirm no .busavelock53 extensions spawn on freshly created files.

3. File Decryption & Recovery

  • Recovery Feasibility: NO decryptor yet for v2.x (Aug 2024 wave). AES-128 in CTR mode with an RSA-2048 session key parceled into config section – and RSA OAEP header scrambled on-the-fly. No known key leakage, and the attacker’s ransom note explicitly references an offline RSA keypair (pubkey.der locally stored).
  • Trial Tools:
  • MeowWare Unmasker v1.6 (built for the earlier v1.0 strain) fails checksum check.
  • ShadowExplorer / Veeam Agent restore if Volume Shadow Copy was not expunged (Busavelock53 does erase VSS by default).
  • Essential Patches:
  • Microsoft KB4499175 (cumulative August 2024)
  • Cisco Advisory cisco-esa-sa-20240305-firmware is no longer sufficient; ensure IOS XE is on post-Oct 2023 patch train.

4. Other Critical Information

  • Unique Characteristics:
  • User-mode file-monkey-driver KalNdr.sys installs only after successful encryption process has concluded (defensive antitweak measure).
  • Target list exclusion skips Russian, Belarusian, and Armenian locales (GetUserDefaultGeoId = 7, 20, 51)—a rarely seen geographic filter.
  • Physically delete jpg/png thumbnails via Windows property handler to hamper baked-in recovery thumbnails.
  • Broader Impact:
  • First major ransomware incident that chained Cisco IOS XE exploit to endpoint ransomware—arguably only a proof-of-concept by a suspected ransomware-as-a-service (RaaS) affiliate.
  • Introduced the “CollabChoice” scheme—victims who pay within 48 h are whitelist-unlocked automatically without supplying an ID, executed by a leaked PowerShell script posted to busavelock53.bit.

Stay vigilant—patches for two of the five main vectors were already available before this ransomware first appeared, underscoring that defense-in-depth patching remains the most cost-effective barrier.