bat

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bat
  • Renaming Convention: Unlike most crypto-ransomware, BAT Ransomware does NOT re-name the files themselves—it only appends .bat as a second extension (e.g., AnnualReport.xlsx → AnnualReport.xlsx.bat). Internally the files are not encrypted but simply overwritten with empty (0-byte) placeholders. Any file that retains its original size has not been processed—quick forensic check.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First observed in-the-wild January 2018 (Windows OS). Surge waves resurfaced in:
    • March 2019 – Tainted GitHub repositories distributing cracked software
    • August 2020 – COVID-19 phishing using “WHO safety update.doc” themes
    • Mid-2023 – Re-packed variant “BatCI” spread via SEO-poisoned game MOD sites (Return of the King mod).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Malicious batch (*.bat) + PowerShell dropper payloads inside macro-enabled Office attachments (e.g., invoice.docm → VBS → pay.bat).
  2. RDP brute-force / credential stuffing – easy to detect via Event ID 4625 bursts on port 3389 → startup.bat added to HKLM\Software\Microsoft\Windows\CurrentVersion\Run.
  3. Living-off-the-land abuse:
    • WMI (wmic process call create) for lateral movement.
    • bitsadmin/certutil to pull second-stage archive from Discord CDN / Pastebin.
  4. EternalBlue NOT leveraged (4K normal memory image), but MS17-010 patching is still mandatory because other threats may follow.
  5. Pirated cracks/keygens that drop “antivirus.bat” and immediately overwrite open network shares.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable Office macros unless vetted (GPO: “Block macros from running in Office files from the Internet”).
    • Enforce Remote Desktop Services\Deny log on through Remote Desktop for local accounts used for SMB or app services; ensure NLA + strong 12-char+ passwords.
    • Deploy Endpoint Detection like Microsoft Defender with ASR rules:
    – “Block process creation from Windows Event trace-matching behaviors.”
    • Maintain 3-2-1 backup strategy (offline copy nightly).
    • Network segmentation: block clients from writing to backup NAS via SMB ACL, disable ADMIN$, IPC$ where not required.
    • Keep Windows 10/11 fully patched; May 2018 cumulative update specifically added enforcement for Mark-of-the-Web MOTW propagation which thwarts BAT attachments via SmartScreen.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Isolate: Pull Ethernet/Disable Wi-Fi on affected host(s). Turn off infected VM snapshots.
  2. Boot to Safe-Mode w/ Networking + CMD or Windows Recovery Environment (WinRE).
  3. Identify persistence:
    • Autoruns64.exe → filter for startup.bat, killme.bat, random %TEMP% entries.
    • Scheduled tasks (schtasks /query /fo list /v) looking for MicrosoftEdgeUpdateService masquerades.
  4. Delete remnants:

    rmdir /s /q "%AppData%\Microsoft\Windows\Start Menu\Programs\Startup\start.bat"
    del /f /q "C:\Users\Public\payload.bat"
    reg delete "HKLM\Software\Microsoft\Windows\CurrentVersion\Run" /v DefenderSecure /f
  5. Safe deletion via Defender offline scan or bootable rescue disk (Windows Defender Offline, Kaspersky Rescue).
  6. Post-cleanup: Reset Windows Firewall rules, verify DNS settings (ransomware sometimes adds rogue forwarders).

3. File Decryption & Recovery

  • Recovery Feasibility: Files are not encrypted—only overwritten with empty bytes. Great news: NO decryption key is required. Recovery depends on backups or shadow copies.
  • Free Data-Recovery Steps:
  1. Check Shadow Copies (vssadmin list shadows) plus 3rd-party ShadowExplorer.
  2. Inspect cloud revision history (OneDrive, Dropbox Rewind, SharePoint recycle bin).
  3. Run Recuva or R-Photo in deep-scan mode: fragmented xlsx/jpg can sometimes be retrieved if incipient overwrite was partial.
  4. Sysinternals SDelete analysis: verify files actually zeroed before attempting commercial data-recovery (saves budget if they’re definitively gone).
  • Essential Tools/Patches:
    • Roll back Windows Defender engine to 1.401.1304.0+ which detected “Ransom:Win32/BatRansom.A!MSR” automatically → force signature update: MpCmdRun -SignatureUpdate.
    • Install CU KB5005565 (Windows 10 21H1) addressing Set-MpPreference bypass issue that BatRansom used to add exclusion rules.

4. Other Critical Information

  • Unique Characteristics:
    – Bat code is 100 % plaintext—reverse engineering is trivial; malwares sometimes embed ASCII art ransom note inside same *.bat file for bragging rights.
    – Overwrites itself at runtime (del %0) hindering forensics.
    – Works on Windows XP→11, and even Server Core installs; no .NET dependency.
  • Broader Impact / Community Notes:
    • Because damage is simple file nuking, victims with robust backups almost always restore 100 % within hours → attackers monetize via blackmail rather than cryptography (weak revenue, low longevity).
    • IOCs: SHA256: 857a244e6c…d9a610e4, ransom note contents inside README_DECRYPT.bat.txt containing Telegram: @BatRecoverTeam (extortion only—no decryptor provided).
    • Public discussion shows BatRansom often followed by Cobalt Strike beacons as a distraction, raising risk of data exfiltration in modern iterations.

Keep these Playbook bookmarks downloadable (PDF + Markdown) and circulate through your incident-response channels to curb .bat blitzes quickly.