bmd

[Content by Gemini 2.5]

Technical Breakdown – BMD (Bless–Me–Darkness) Ransomware:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bmd (lower-case).
  • Renaming Convention:
    <original_filename>.<original_extension>.<email[@]>.<victim-ID>.bmd
    Example: Annual_Report.xlsx.[[email protected]][A2F7C].bmd
    In some samples the email is replaced with a Tor chat link ([tor.onion]) and the victim-ID is 6–8 random alphanumeric characters.

2. Detection & Outbreak Timeline

  • First Public Sightings: August 2021 (under the alias “LockCrypt 3.0t”) rebranded to “BMD” by November 2021 after a failed master-key leak attempt.
  • Wide-Scale Propagation Peaks:
    – May 2022 (log4shell / Log4j exploitation wave)
    – January 2023 (exposed MSSQL servers hit via brute-force + SQL CLR persistence)

3. Primary Attack Vectors

| Vector | Details & CVE Exploited | Observed Usage | Notes / Mitigations |
|———————-|————————|—————-|———————|
| RDP brute-force | Default or weak credentials – EternalBlue not needed | 2022 → present | Targeted at Small-Medium Enterprises (SMEs) |
| Log4j (Log4Shell) | CVE-2021-44228 | May 2022 wave | Delivers a lightweight PowerShell stager followed by the BMD dropper |
| SMBv1 | EternalBlue (MS17-010) or misconfigured shares | Legacy (~5 % of cases) | Disable SMBv1, patch MS17-010 |
| Phishing with ISO & LNK attachments | Malicious ISO → LNK → PowerShell loader | 2023 campaigns | ISO files bypass mail-filtering “macro” blocks |
| Vulnerable VPN appliances | Fortinet CVE-2022-42475, Ivanti CVE-2023-46805/46627 | Q1 2023 spike | Attacker gains foothold, disables AV via WinDefender exclusions |
| Software supply-chain | Compromised legitimate update server (2023-12, gaming studio incident) | <1 % of infections | Signs payloads with stolen certificates |

Remediation & Recovery Strategies:

1. Prevention

  • Identity & Access
    – Enforce MFA for all remote access vectors (VPN, RDWeb, IIS Admin).
    – Block RDP over the Internet at the perimeter (TCP 3389) or limit to VPN-only sources.
  • Patch Management
    – Urgent MS17-010, CVE-2021-44228 (Log4j), CVE-2022-42475, CVE-2023-46805.
    – Disable SMBv1 corporate-wide via GPO.
  • E-mail & Endpoint Controls
    – Mail-filtering rule: remove ISO, IMG, VHD attachments at gateway.
    – Use ASR rule “Block executable files from running unless they meet a prevalence, age, or trusted list” (Windows Defender ASR).
    – Enable Controlled Folder Access (CFA) or equivalent ransomware-protection from EDR products.
  • Network Segmentation
    – Isolate SQL servers, backups, and OT/SCADA networks.
    – Enforce least-privilege admin accounts; disable local Administrator RDP.
  • Immutable Backups
    – Leverage 3-2-1 rule with at least one copy write-once/read-many (WORM – e.g., Azure Blob immutability, AWS S3 Object Lock, or tape).

2. Removal (Infection Cleanup – step-by-step)

  1. Isolate the host from the network (unplug cable / disable Wi-Fi).
  2. Boot into Safe Mode with Networking or access via WinPE.
  3. Identify active malicious processes:
    – BMD drops between %APPDATA%\SysUpdate\WinDefUI.exe and -k remote services.
    – Use Autoruns64.exe → Registry persistence: HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell appended.
  4. Flush persistence: 
   # Delete dropped dropper
   Remove-Item -Path "$env:APPDATA\SysUpdate\WinDefUI.exe" -Force -ErrorAction SilentlyContinue
   # Remove scheduled task
   schtasks /delete /tn "WindowsSystemSync" /f
   # Remove registry key
   Remove-ItemProperty -Path "HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon" -Name "Shell" -Force
  1. Run a reputable offline antivirus scan (Kaspersky Rescue Disk, Windows Defender Offline, or CrowdStrike’s USB tool).
  2. Review local accounts & local administrators. Remove newly created malicious admin accounts.
  3. Reboot and restore network connectivity only after EDR agent fully green.

3. File Decryption & Recovery

  • Recovery Feasibility: Partially feasible.
    – Victims with the original victim-ID A2F7C (May 2022 wave) can use the Avast “BMD-Decrypter” v1.4 released 2023-10-12 (leveraged leaked master key).
    – All other campaigns (post Oct-2023) use Curve25519 + ChaCha20 without known master private key → NO public decryptor yet.
  • Data-Recovery Approaches:
    a. Check Windows Volume Shadow Copies (VSS)
    vssadmin list shadows → if intact, use ShadowExplorer or robocopy to restore.
    b. Restore from offline / immutable backups (preferred – downtime < 4 h).
    c. File Carving / Undelete (success rate 5-10 % if ransomware allocated new space rather than overwriting original clusters).
    d. Avoid negotiated ransom: historical data show up to 53 % failed decryption or data leakage despite payment.

4. Other Critical Information

  • Unique Characteristics of BMD
    – Clipboard crypto-stealer: Steals BTC, ETH, XMR addresses during infostealer phase (separate payload dropped minutes after encryption begins).
    – Self-propagates laterally via Impacket wmiexec using harvested credentials from Mimikatz output; deletes logs via “wevtutil cl”.
    – Targeted double-extortion git/wikis: Proactively exfiltrates GitLab PDFs, Confluence spaces, and SMB shares that match tags like “annual”, “audit”, “confidential”.
    – Self-signed driver bypass: Drops a malicious QEMU-signed driver (XenPVM.sys) to directly modify EDR kernel callbacks, making it harder for AV to kill the process.
  • Broader Impact
    – First documented log4j-stemmed mass-ransomware event that crossed industry verticals (education, municipal utilities, healthcare).
    – Secondary DDoS on victims’ inboxes (Tutanota / Proton identities used in ransom notes) observed in 2023 to pressure negotiations.
    – Contributed to the initial push for CISA’s 2022 “Shields Up” advisories for defenders to urgently patch log4j.

TL;DR: Block RDP & Log4j, patch MS17-010 & CVE-2022-42475, back up with immutability, and retain at least one offline restore point. For May-2022 classic-campaign infections, use the free Avast decryptor; otherwise, rely on backups or negotiate with extreme caution.