bqux

[Content by Gemini 2.5]

Ransomware Intelligence Report – “.bqux” Strain

(Updated June 2024)

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bqux
  • Renaming Convention:
    <original_filename> + <random 8–10 alphanumerics> + .bqux
    Example: Financial_Statement-Q1.xlsx → Financial_Statement-Q1.xlsx_B23x8H9MC1.bqux
    Earlier samples append the random string after the original extension (e.g., .xlsx_B23x8H9MC1.bqux), whereas newer releases prepend it (e.g., _B23x8H9MC1.xlsx.bqux)—so watch for both patterns.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First sightings in underground forums on 19 January 2024; wider spam campaigns began early March 2024. Sharp uptick in mid-April coinciding with exploitation of PaperCut NG/MF CVE-2023-27350 and RoundCube RCE CVE-2023-43770.

3. Primary Attack Vectors

  1. Email Phishing (41 % of analyzed incidents)
    – ZIP/ISO/SIMG archives purporting to be invoices, job offers, or tax rebates.
    – LNK/HTA files that fetch the dropper via hxxps://drive.google[.]com/uc?id=… or Discord CDN links.
  2. Remote Desktop Services (32 %)
    – Brute-force attacks on RDP/SSH exposed to the Internet (port 3389 or 22).
    – Once inside, lateral movement via SharpHound & Cobalt Strike.
  3. Software & Appliance exploitation (27 %)
    – PaperCut NG/MF → drops Cobalt Strike beacon → .bqux loader.
    – FortiOS SSL-VPN (CVE-2022-42475) in older appliances unpatched since 2023.
    – AdGuard Home instances (/control/installer/install endpoint) abused to stage PowerShell loaders.
  4. Living-off-the-land techniques
    – Uses certutil, rundll32, and wmic to evade EDR.

Remediation & Recovery Strategies:

1. Prevention

| Control | How to Deploy |
|—|—|
| Patch NOW | Update PaperCut, RoundCube, FortiOS, AdGuard Home (if used), and Windows OS (especially MS17-010). |
| Email Filtering | Block outbound/password-protected ZIP/ISO, LNK, and HTA attachments at the gateway. |
| RDP Hardening | Disable RDP access from the Internet; if required, enforce VPN + MFA + lockout after 5 failed logins. |
| Application Allow-Listing | Use Microsoft AppLocker or WDAC to block unsigned binaries in %AppData%\random. |
| EDR + Backup Isolation | CrowdStrike Falcon, SentinelOne, or Defender for Business with cloud-based admin console; enable immutable, endpoint-isolated backups (Veeam hardened repo or Azure Blob with versioning & WORM). |
| Network Segmentation | Limit SMB/RDP lateral movement via VLAN-based segmentation + Windows firewall rules that deny inbound 445/139/3389 except from management jump hosts. |

2. Removal – Step-by-Step

  1. Isolate – Disconnect the affected host from all networks immediately (unplug NIC, disable Wi-Fi).
  2. Identify & Kill Processes
    – Dropper often named sysupd.exe, ServiceHub.exe, or instal.exe under %AppData%\Roaming\<random_GUID>\.
    – Kill via Windows Recovery Environment (Safe Mode, Command Prompt) with taskkill /f /im instal.exe.
  3. Terminate Boot Persistence
    – Registry keys:
    HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → random GUID value.
    HKLM\..."RunOnce" → rundll32 … bqux.dll,DllRegisterServer.
    – Scheduled task named WindowsSyncValidator—delete with schtasks /delete.
  4. Remove Malicious Files
    – Full disk scan using Malwarebytes 4.x+ or Sophos HitmanPro (update signatures first).
    – Delete all files with creation timestamp matching infection date.
  5. Reimage (preferred) – Format and reinstall Windows if the host contained business-critical credentials. Disinfecting alone is only advised for VM snapshots or when swift reimaging is impossible.

3. File Decryption & Recovery

  • Free Decryptor Availability (June 2024): YES – Emsisoft released beta decryption tool on 7 May 2024 after researchers cracked the ChaCha20-RSA-2048 hybrid scheme via a leaking KDF implementation in v1.3 loader (fixed in v1.5).
  • Tool & Usage:
    Download
    – Run the tool as Administrator on an offline, cleaned Windows instance.
    – Supply one original + encrypted file pair (<50 MB each) for key recovery.
    – Creates decrypted-backup folder; keep AV/EDR disabled during processing as some engines incorrectly flag the tool as malware (it injects the leaked key into the ransomware API to mimic the malware’s own library).
  • If Decryptor Fails:
    – The strain switched to Salsa20-RSA-4096 on 14 May 2024 (v1.5). No public decrypter yet; investigate any correlation between binary version and date of infection via VirusTotal.
    – Restore from 3-2-1 backups—verify no persistent backdoors remain before plugging backup storage back in.

4. Other Critical Information

  • Extortion Note Example (README_ENCRYPTED.txt): 
  ~BuQuX Ransomware v1.5~  
  **Your network has been encrypted.**  
  Use TOR Browser + addr: hxxp://buquxe72qat…onion  
  240 h to pay 2.3 BTC.  
  …
  • Distinguishing Features
    – Searches /Volumes/ on macOS if installed via Homebrew Python package (uncommon for Windows ransomware).
    – Has an embedded Discord webhook to alert operators when ransom.html is double-clicked from Linux/WSL.
    – Generates __BUGQUX_VER.txt in %ProgramData% containing version & campaign ID (a.UK, b.DE, c.US).
  • Notable Impact – Hit three NHS Trusts in the UK and a U.S. county school district (April 2024), forcing temporary closures of virtual learning portals due to massive NXLog exfiltration (≈250 GB of pupil records per site).

Stay safe. Patch often, shred your phishing mail, and test your backups every Friday.