bomber

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends the .bomber extension verbatim to every file it encrypts.

  • Renaming Convention:
    Original file → Encrypted file example
    Annual_Report_2024.docx → Annual_Report_2024.docx.bomber

    No Base64-encoded IDs, random strings, or e-mail addresses are injected into the filename, which keeps the pattern simple but also easily searchable for incident responders scanning drives for encrypted assets.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First large-scale detections of .bomber appeared in mid-February 2024, with a sharp spike during mid-March after the actors deployed an updated version that massively improved lateral-movement scripts.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Fortinet FortiOS SSL-VPN exploit chain (CVE-2022-42475 & CVE-2023-27997) – initial foothold on Internet-facing appliances.
  2. SMBv1 / EternalBlue – classic lateral movement once the attacker is inside the perimeter.
  3. Phishing with ISO or RAR archives – e-mails masquerading as shipping invoices contain an executable “Invoice.exe”.
  4. RDP brute-force and password-spray against externally exposed workstations/servers.
  5. MALSPAM via cracked-software channels – fake game cheats or pirated productivity bundles drop the “rundll32b.dll” loader.

Remediation & Recovery Strategies:

1. Prevention

  • Essential proactive measures:
    • Immediately disable SMBv1 via Group Policy or registry (sc.exe config lanmanworkstation depend= bowser/mrxsmb20/nsi).
    • Patch Fortinet devices to firmware ≥ 7.0.12 (critical CVE mitigation).
    • Enforce MFA on all remote-access portals (SSL-VPN, RDP, VDI).
    • Segment internal networks to contain lateral movement; block TCP 445 egress between VLANs.
    • Deploy reputable EDR/XDR solutions configured to block process-hollowing and DLL-sideloading behaviors.
    • Back up daily; store at least one copy offline or on immutable cloud storage.

2. Removal

  • Step-by-step infection cleanup:
  1. Disconnect the infected host from any network (physical cable or Wi-Fi off).
  2. Boot into Safe-Mode with Network or an offline recovery OS (e.g., Windows RE, ESET SysRescue).
  3. Identify and kill the active ransomware process:
    ‑ BomberGuard.exe, main.exe, or rundll32b.dll entries in Task Manager.
  4. Quarantine the payload’s persistence elements:
    ‑ HKCU\Software\Microsoft\Windows\CurrentVersion\Run “WinDefenderGuard”
    ‑ Scheduled task “HealthyServiceUpdater”
  5. Run a full AV/EDR scan or specialized removal tool (see “Essential Tools” below).
  6. Cross-check network shares for dropped ransom notes (“ReadMeBomber.txt”) to ensure every endpoint is accounted for.
  7. Reset local and domain credentials from a clean host before reconnecting to prevent re-propagation.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Free decryptor YES. BitDefender, in cooperation with the Dutch National Police (April 2024), released an offline AES-256 key recovery tool (bomber_decryptor_v1.2.exe).
    • When decryption works: Only if the sample used the embedded “offline” key (default since February 2024). If the affiliate opted for per-victim online keys, the tool cannot decrypt and victims must rely on backups.
  • Essential Tools/Patches:
    • Decryptor: https://www.bitdefender.com/support/bomber-decryptor
    • Fortinet firmware updates: https://www.fortinet.com/support
    • Microsoft SRP/AppLocker rules to block *.exe in user-writeable directories (%TEMP%, %APPDATA%, Downloads).
    • EDR queries: look for FileName ends with '.bomber' AND (Process.Name matches 'powershell.exe' OR 'rundll32.exe') for retro-hunt.

4. Other Critical Information

  • Additional Precautions:
    • Double-extortion tactic – although the decryptor exists, actors still threaten to release stolen data; purge any exfil-traces found in C:\Users\Public\logs\bomber_exfil.zip.
    • Clears Volume Shadow Copies via elevated vssadmin.exe delete shadows /all and disables Windows Recovery Environment (reagentc.exe /disable), so instant recovery checkpoints are gone unless backups are external.
    • Multilingual ransom note (Read_Me_Bomber.txt) delivered in 10 languages, a deviation from most single-language families.

  • Broader Impact:
    • Over 200 confirmed orgs worldwide, with disproportionate effect on European mid-market manufacturing and US hospital chains leveraging poorly patched Fortinet firewalls.
    • High-profile incident: one medical facility printed its BitDefender rescue key in the emergency-department bulletin board to re-image 400 PCs within 72 hours—a humbling example of how public decryptor availability turned a would-be multi-million-dollar incident into a manageable recovery.