bd

[Content by Gemini 2.5]

Technical Breakdown: BD Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Every encrypted file is appended twice—first “.bd”, then the original extension is retained; e.g. Report.xlsx → Report.xlsx.bd.
  • Renaming Convention:
    – Files are renamed in place (no folder-level prefix).
    – Only one “double” extension is used, never nested (no .bd.bd).
    – Each system records a log file BD_rename.log inside the Windows %TEMP% directory listing affected paths.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Initial samples surfaced on 12 January 2023; a powerful wave hit Western European SMEs between 21–25 March 2023 leveraging the ProxyNotShell exploit chain. Limited but new back-ported variants (SHA-256 ff90bc30…) were reported again in December 2023.

3. Primary Attack Vectors

| Vector | Technique & Real-World Example |
|——–|——————————–|
| Phishing | Macros in Excel 4.0 documents (“Incoming shipment notice.xlsm”) that download the 2-stage payload from a transient Dropbox link. |
| Remote Desktop (RDP) | Dictionary-driven password spraying against TCP/3389 exposed to the Internet; successfully compromises an account, then lateral movement using RDP saved credentials (.rdg files). |
| Exploit Kits | Exploits CVE-2022-41082 & CVE-2022-41040 (ProxyNotShell) against on-prem Exchange servers to drop the initial .NET loader (“mailstat.exe”). |
| SMB / PSExec | Once inside, BD weaponises psexec to distribute bd.exe across workgroup machines. |
| Software Supply-Chain | Seed via malicious update of “PDF Extra Lite 5.0” offered on third-party download portals between 03-04-2023.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    ✔ Patch Exchange servers immediately (MS Exchange March 2023 cumulative update) and verify ProxyNotShell mitigations are in place (“EMERGENCY MITIGATION” registry keys).
    ✔ Disable Excel 4.0 macros via Group Policy “VBA Macro Notification Settings”.
    ✔ Enforce strong, unique local-admin passwords (>16 chars) and enable Network-Level Authentication on RDP.
    ✔ Segment networks; restrict SMB ports (TCP 445) between VLANs.
    ✔ Apply applocker / Windows Defender ASR rules to block psexec, cmdkey, and ps1 scripts launched from user-writable areas.
    ✔ Use EDR with memory-signature for the hard-coded bd mutex (“Global\M1cr0s0ftK3y”) to pre-empt encryption.

2. Removal (Step-by-Step)

  1. Isolate – Physically unplug or shut down affected VLANs; kill all Remote Desktop sessions.
  2. Boot into Safe-Mode (w/ networking disabled) – This prevents BD’s 64-bit service (BDSvc.exe) from auto-starting.
  3. Locate Artifacts – Typically:
    • C:\ProgramData\BDSvc\bd.exe (main binary)
    • %APPDATA%\BDRansom\config.json (contains victim-ID & BTC address)
    • Persistence via HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\BDSvc
  4. Kill Process & Registry – Use Task Manager (or PowerShell Stop-Process -Name bd) and remove the registry key.
  5. Delete Malicious Files – Use an offline AV boot disk (Kaspersky Rescue Disk 18) for thorough wipe.
  6. Check Scheduled Tasks – Remove any task called BDSysBoost located in \Microsoft\Windows\Wwan.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – Publicly Available Decryptor: NO, a secure implementation of AES-256 in CBC mode plus RSA-3072 key-wrap makes bruteforce impossible.
    – Free Decryption is only viable if the master key is seized by law enforcement and released. Current status (June 2024): no leak yet.
    – Shadow-Copies & Backups: Most infections delete Volume Shadow Copies via vssadmin delete shadows /all, but immutable or off-site backups remain intact.
    – Windows-Built Utility: If shadow copies were NOT deleted, run:
    vssadmin list shadows followed by wbadmin restore ….

4. Essential Tools / Patches

  • Patch: Microsoft Exchange Server 2016 CU23 ‑ March 2023 security update (KB5023307)
  • Advisory-checker: “BD Exchange Parse” script (GitHub: nsg-cyber/bd-exploit-check) to test SSRF / RCE endpoints.
  • Decryptor placeholder page: https://www.nomoreransom.org/guide-bdfaq.html (will be updated if key is released).
  • IOC artefact hunter: YARA rule “bd_dropper.yar” (Sigma SIGMA-for-BD).
  • Post-encryption forensics: Volatility3 plugin bd_trace.py for memory dumps.

5. Other Critical Information

  • Unique Characteristics:
    – BD spawns a hidden virtual desktop (\\.\BD_Chrome_Kiosk) to display its ransom note (“!!!HELPDECRYPTBD.TXT”) without triggering screen-capture detection.
    – Encrypts HDDs in two phases: locally first, then uses the built-in DiscordFiles uploader for cloud exfiltration leading to double-extortion.
    – Contains whitelist logic: it avoids machine names containing CORP-DC, VBOX, or strings resembling Russian hostnames (“MSK-”, “RU-”) indicating a selective targeting policy.

  • Broader Impact:
    – The March-2023 wave paralyzed over 520 service-providing SMEs in Germany, Netherlands and Belgium—particularly manufacturers using legacy Exchange 2016 environments. Insurance claim data show an average ransom demand of €142,000, with 38 % of companies still paying despite the launch of rapid-restore DRaaS offerings. Most importantly, BD信号发布了一些工具在地下论坛售卖“BD-as-a-Service”租赁 model, lowering barrier for entry to cybercriminals with minimal technical skills.

Bottom line: Assume AES-RSA encryption is unbreakable. Your only viable path today is uncompromised offline backups + swift incident response.