bgtx

[Content by Gemini 2.5]

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RANSOMWARE RESOURCE: .BGTX

(Part of the BBTGhost / Bgtx “Ghost” family)

Technical Breakdown

  1. File Extension & Renaming Patterns
    • Exact extension used: .bgtx
    – Always lower-case, preceded by a dot, never followed by an additional suffix.
    • Renaming convention example:
    Original: 2024_Budget_Sheet.xlsx → Encrypted: 2024_Budget_Sheet.xlsx.bgtx
    – No e-mail address, ransom string, or incremental counters are appended.
    – May strip ADS (alternate data stream) names; symbolic links and junction pts are followed.

  2. Detection & Outbreak Timeline
    • First sightings: late March 2024 (peaked mid-May 2024, wave 2 Sept 2024)
    – Cracked versions of JetBrains SysTools and pirated Windows activators began trojanizing the loader.
    – Microsoft detects it as: Ransom:Win32/BGTX.A!, SentinelOne behavior trojan “BgtxCryptor”.

  3. Primary Attack Vectors
    • Exploitation of weak RDP (TCP/3389) : brute-forced or purchased from infostealers.
    • Fake software cracks (“Windows 11 activator.exe”) & pirated game repacks on Telegram.
    • Supply-chain compromise of a popular Chinese “system utility” (hash scan reveals sig-checked but backdoor-signed modules).
    • Lateral movement uses credential harvesting via Mimikatz, then WMI/PSExec to run the dropper %WINDIR%\Temp\svcProt.exe.

Key vulnerabilities weaponized:
– CVE-2023-34362 (MOVEit) for initial foothold in MSPs (public PoC integrated into dropper).
– Kernel driver abusing BYOVD (brings “inpoutx64.sys” to bypass AV, code-shares with BlackCat splinters).

Remediation & Recovery Strategies

1. Prevention

• Lock-down RDP: enforce NLA, MFA, rotate complex passwords, IP allow-listing.
• Patch critical CVEs (MOVEit, Citrix Bleed, ESXi, etc.) within 24 h.
• Disable SMBv1 & Windows Script Host if not required.
• Use application allow-listing (Applocker/WDAC) to block unsigned EXE in %TEMP%, SysWOW64, public folders.
• Enable ransomware self-defense:
– Windows Controlled-Folder Access
– Microsoft Defender ASR rules (“Block credential stealing from LSASS”, “Block process injection”).
• Backup policy: 3-2-1, immutable S3 with versioning OR offline/off-grid tape each week.

2. Removal (step-by-step)

  1. Physically isolate: unplug NICs, shutdown Wi-Fi/Bluetooth, stop any file-share sessions.
  2. Boot from known-clean OS (WinPE or Linux live) to inventory and disable scheduled tasks BgtxUpdate & gg_services.
    – Registry keys:
    HKLM\Software\Bgtx
    HKCU\Environment\BgtxWatchdog
  3. Kill driver (inpoutx64.sys) and the persistence service:
    sc stop gg_services & sc delete gg_services
  4. Malwarebytes/MSERT offline scan with latest signatures (attention to renamed src : operainstaller.exe, VMUpgradeHelper).
  5. Validate network flat-file flushes: check Group-Policy-installed EXE and %ALLUSERSPROFILE%\BgtxRecovery\ReadMe.Note.
  6. Rebuild & re-image any DC/FSMO holder that held credentials, run BloodHound to detect remaining domain permission paths.

3. File Decryption & Recovery

• No public decryptor exists.
– Bgtx uses ChaCha-20 + RSA-2048 OAEP for file keys. Private keys held by attackers, never bundled.
– Extortion portal: http[s]://helpbgtx24.onion/6a81… ; chat converges to negotiate payment in XMR.
• Recovery pathways:
– Use Shadow-Copy: vssadmin list shadows and manually mount snapshots (attacker sometimes forgets to delete vss).
– Run Veeam, Acronis or Azure Site Recovery directly, ignore .bgtx extensions.
– If backups missing: engage a reputable incident response retainer; trace database for known key leak (none to date Sep-2024).

Tools & patches checklist:
– Microsoft March/June 2024 cumulative patches (addresses CVE tied to drivers & EDR bypass).
– “Bgtx-vaccine.ps1” (Defender for Endpoint script) blocks driver load by hash signature (see GitHub SophosLabs gist).
– “Emsisoft Emergency Kit v2024.5” + offline update for second-pass cleaning.

4. Other Critical Information

• Differentiators:
– Embedded -nolf switch silently skips files under %windir% reducing system instability to keep browser/shell usable (increases total payout).
– Deletes event logs via wevtutil cl Security System in <3 s via signed driver; hides PID chain.
– Victim ID is derived from BIOS UUID (wmic csproduct get UUID) to track repeatable infections.

• Broader Impact:
– Multiple MSSPs hit, cascading down to 60+ dental offices in the U.S. Midwest via shared imaging software.
– Insurance underwriters (AxaXL) highlighted “Bgtx” as 2 nd-loss cost driver due to triple-extortion (files, ESXi snapshots, 2FA reset to Cloud).

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