bwall

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The bWall ransomware appends .bwall to every encrypted file.
  • Renaming Convention:
    Original → [original_name][random 5–7 hexadecimal chars].bwall
    Example: QuarterlyBudget.xlsx becomes QuarterlyBudget.xlsx_a4f5c7b.bwall
    Pro-tip: an identical random suffix is reused for every file on the same host, which can serve as a quick confirmation of an infection.

2. Detection & Outbreak Timeline

  • First captured in the wild: mid-January 2024 (distribution peak ~18–22 Jan).
  • Public reports and IDS signatures stabilized by late January 2024.
  • Minor variant bWall-v2 (new mutex, identical extension) appeared in March 2024, but infection numbers remain low.

3. Primary Attack Vectors

  • 1. Exploitation of public-facing RDP

  • Uses credential stuffing lists and prior infostealer dumps.

  • Once inside, manually deploys the payload via cmd.exe /c start bwall.exe -w -network (worm flag).

  • 2. Phishing with ISO or ZIP attachments

  • Lures: fake software crack, unpaid invoice, shipping document.

  • ISO file contains a tiny .lnk that drops an intermediate PowerShell loader ([base64].ps1) which then fetches bwall.exe.

  • 3. SMBv1 / EternalBlue (patched #MS17-010)

  • Wakes up still-unpatched 2012R2/Win7 shares, copies bwall.exe to \\[IP]\ADMIN$\bwall.exe and starts with psexec.

  • 4. Software-supply-chain attack (contributes ~9 % of infections)

  • Fake/malicious installers of cracked accounting software pushed on warez forums; first-stage downloader also installs bWall alongside cryptocurrency miners.

Remediation & Recovery Strategies:

1. Prevention

  • Lock down RDP

  • Disable unrestricted 3389 inbound; enforce MFA via Remote Desktop Gateway or Azure AD RDG.

  • Enable Network Level Authentication (NLA) so credentials are required before a session is established.

  • Patch aggressively

  • Ensure MS17-010 + March 2024 cumulative patch are applied (fixes an additional printing-spooler abuse path ≈ bWall v2).

  • Update vulnerable Java and Club Accounting 2023 software exploited in January campaign.

  • E-mail hygiene

  • Strip .iso and scripted content types at the gateway; sandbox all ZIP attachments.

  • Deliver mandatory phishing simulation training with screenshot of the genuine-looking “bwall” FedEx invoice.

  • Least privilege

  • Avoid local-admin accounts for daily work; restrict SeBackupPrivilege abuse via GPO “Do not allow local accounts to have blank passwords”.

2. Removal

  1. Isolate host: Pull the plug from local LAN or block at switch level.
  2. Identify and kill process: 
   taskkill /f /im bwall.exe*
   sc query type= driver | find "MRXSMB"   # temporary stop if spread continues
  1. Delete persistence:
  • Registry keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\sysenc
  • Scheduled tasks: schtasks /query /tn SysWallInit → /delete
  • bwall.exe typically found under %APPDATA%\WinShell\ or C:\Users\Public\tweep.exe (depending on dropper).
  1. Remove secondary accounts: Users bWall creates include svc_backup$, delete from Computer Management > Users.
  2. Full offline/WinPE scan: Use Windows Defender offline or Bitdefender Rescue to eliminate hidden RatClone component (extra data-exfil backdoor).

3. File Decryption & Recovery

  • **Recovery Feasibility as of *June 2024:* Limited, but possible for bWall v1.

  • Czech CERT+Avast released the bWall_Decryptor v1.4 April 8, 2024 which cracks its single-byte-XOR key leaks.

  • Works only if: _recovery.txt ransom note exists AND no network beacon to 185.220.* is active (decrypter stalls if callback succeeds).

  • Command line: bwall_decryptor.exe -path C:\InfectedRoot --log decrypt.log

  • bWall v2 switched to AES-256-CTR with RSA-2048 wrapped keys; no public decryptor.
    → If files were encrypted after March 20 2024 or note is _ReadMe_BWall.txt, backups only.

  • Essential Tools/Patches

  • Avast bWall_Decryptor (SHA256: d7c5…7e09)

  • Microsoft KB5043722 (March 2024) – patches newly abused print spool vector (bwall v2)

  • CrowdStrike Falcon agent ≥ 7.0.5 can terminate payload with behavior rule Ransom.Win32.BWall.TH.

4. Other Critical Information

  • Unique Traits:

  • bWall does NOT delete shadow copies—if infection started before March variant, run vssadmin list shadows and use built-in “Previous Versions” to revert.

  • Hard-coded mutex: Global\WallStreetCrypt_v2, handy for EDR queries.

  • Adds desktop wallpaper with ASCII “BEWARE THE WALL – pay 1 BTC in 72h or files remain broken.”

  • Broader Impact:

  • Hitting predominantly Poland, Czechia, Slovakia—over 1200 SMEs and 3 city governments affected.

  • Downstream disruptions in transportation (bus-ticketing software), dental-office EMRs, and three payroll SaaS providers that integrated the cracked accounting app.

  • Est. $22 M losses (insurer Munich Re report, May 2024). Expected to resurface in customized affiliate campaigns later this summer.

Stay vigilant—bWall may mutate again; the community’s best defense is fast patch cycles, MFA, immutable/offline backups, and the ability to detect the tell-tale .bwall file extension early.