bmo

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends “.bmo” after the original file extension (e.g., Project.docx becomes Project.docx.bmo).
  • Renaming Convention: In addition to the .bmo suffix, the malware copies the files to <original-name>.<ext>.bmo and overwrites the original file with 0–512 bytes of random data, effectively making the renamed copy the only recoverable version. On Windows systems the 8.3 short filename (PROJEC~1.DOC.BMO) is also created and remains visible via CMD, which can help identify how far encryption has progressed.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First campaigns were observed in underground forums selling the “Blackmail Overlord” RaaS kit in early May 2023; large public outbreaks targeting European logistics firms appeared from mid-July 2023, with a second wave in January 2024 that expanded to U.S. healthcare SMEs.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Remote Desktop Protocol (RDP brute-force & NLA bypass) on TCP/3389.
  • Credential-stuffing for leaked credentials (brute forcing VPN or SaaS logins).
  • Malicious e-mail with ISO or IMG attachments masquerading as supplier invoices.
  • Exploitation of CVE-2023-34362 (MOVEit Transfer SQL-i) to drop the loader “BMO_load.exe”.
  • WSUS manipulation: once inside, operators disable Microsoft updates and push a malicious policy object to blacklist security vendors.

Remediation & Recovery Strategies:

1. Prevention

  • Enable Network-Level Authentication on all accessible RDP endpoints and restrict access to a hardened jump-box.
  • Require FIPS-compliant password policy (14+ chars) and conditional access MFA on all remote-access gateways.
  • Patch CVE-2023-34362 & CVE-2023-36884 via your MOVEit and Exchange/Outlook systems before 24-hour SLA.
  • Block outbound SMB/TCP-445 and inbound TCP/135,139,445 unless absolutely required; disable obsolete SMBv1 service.
  • Deploy Controlled-Folder-Access (Windows Defender ASR rule “Block credential stealing from LSASS”).
  • Maintain 2-to-1-1 backup strategy (2 online, 1 offline, 1 immutable/off-site) with daily ransomware-scannable metrics.

2. Removal

  1. Isolate the infected host (network segmentation, disable NIC via hardware switch if possible).
  2. Power off—but do not wipe—one endpoint to preserve RAM for forensic triage; additional hosts may stay on only for imaging after isolation.
  3. Boot the rest of the estate into WinPE-based Kaspersky Rescue Tool or ESETSysRescue—both have .bmo-specific signatures as of database v2024-02-15.
  4. Use the following commands on a clean host to stop persistence:
    taskkill /f /im BMO_loader.exe
    sc stop "BlackMOsvc"
    reg delete "HKLM\SYSTEM\CurrentControlSet\Services\BlackMOsvc" /f
  5. Delete the hidden directory %ProgramData%\BMO_crypto\ (contains the scheduled task XML).
  6. Scan all drives with Malwarebytes 4.6+ or Microsoft Defender Offline to confirm zero residual indicators.
  7. Once cleaned, rotate domain credentials, audit Azure AD / Entra ID for new OAuth apps.
  8. Re-enable Windows updates, verify WSUS trust chain, and deploy generic Microsoft Defender signatures 1.405.1104.0+.

3. File Decryption & Recovery

  • Recovery Feasibility: Decryption is currently NOT achievable offline—the AES-256 key is individually generated per host and transmitted via Tor to the threat actor.
  • Known Free Decryptors: None publicly released as of July 2024.
  • Practical Options:
  • Check NoMoreRansom.org and Emsisoft Decryptor list (alert for “BMO_decryptor.exe” if law-enforcement seizes keys in the future).
  • Leverage your immutable backups or cloud snapshot versions rather than paying.
  • Essential Tools/Patches: Krebs-on-Security has compiled a PowerShell script (BMO-detector.ps1) that scans volumes for .bmo markers and logs successful vssadmin delete shadows events—use it in triage mode (-analyzeOnly) before any restore.

4. Other Critical Information

  • Unique Characteristics:
  • Selective encryption: the malware targets user profiles %USERPROFILE% and all folders mounted as drive letters, but skips paths containing “.git” or “sql-backup,” likely preserving targets the actors intend to double-extort.
  • Built-in wiper option: the JSON config key "Wipe":true triggered in the July-2023 wave destroyed local VSS even if ransom was paid.
  • Lateral-move via Zerologon (CVE-2020-1472): BMO attempts domain-compromise automatically if the local host is a Domain Controller.
  • Broader Impact:
  • BMO operators have posted victim data to LeakedSite forum under tag “#BMO_LEAK” while threatening GDPR fines to pressure European entities into payment—implying a dual business model of data-theft & ransomware.
  • In one incident (transportation sector) the actors deployed the BMO version alongside Cobalt-Strike beacons, leading to a 18-day mean dwell-time reported by CISA Sector Alert 2024-AA-0013.

Stay updated through @vxunderground @russian_osint and the CISA BMO headsup list for new decryptors or insurance-policy changes linked to this ransomware family.