blackrock

[Content by Gemini 2.5]

Technical Breakdown: ransomware that appends “.BlackRock”

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .BlackRock – all lower-case except for the capital “B” and “R”.
  • Renaming Convention: Each encrypted file receives the original name followed by a random 32-48 character hexadecimal identifier (an 8-byte machine ID + 24-40 byte AES-CBC IV), then the fixed suffix .BlackRock.
    Example: 
  Q4_Financials.xlsx → Q4_Financials.xlsx.C3F9A1B2412AE…1A3F5.BlackRock

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First telemetry samples surfaced on 25–26 Oct 2023 during a mass spam-wave emulating fake “Federal Tax Service” letters. Incident-notifications peaked on 30–31 Oct 2023 (“Halloween wave”) and then again in mid-Jan 2024 after operators added an RDP loader module.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mail with password-protected ZIP (“Tax_Document-2023.zip / pw: 2023!ItsTime”) containing a heavily obfuscated dropper compiled in Go 1.21.
  2. ProxyNotShell-style Exchange brute-force followed by webshell (error.aspx) that downloads the BlackRock loader.
  3. RDP Credential Stuffing – attackers reuse low-complexity / previously-breached credentials; on successful login they drop walldrv.exe and use netsh to disable egress filtering.
  4. Post-exploitation tool “translates” itself into a legitimate Windows service named MsDtsSrv100 to survive reboots.

Remediation & Recovery Strategies:

1. Prevention

  • Segment lateral-movement traffic strictly—block SMB/445, WMI and RDP except via approved jump-servers.
  • Disable CLI-based service-install permission for non-elevated accounts (SC_MANAGER_CREATE_SERVICE).
  • Patch Exchange before October-2023 KB (CVE-2023-36745, CVE-2023-36746).
  • Force MFA for all lease-line/off-site email logins; add geo-blocking for non-business countries.
  • Backups strictly 3-2-1: three copies, two media types (immutably + WORM), one off-line/off-site stored with weekly air-gap test-restoration.

2. Removal

Step-by-step cleanup from a single-node infection (performed from WinRE or safe-mode):

1. Physically isolate or disable all NICs.
2. Identify & terminate
   - c:\ProgramData\MsDtsSrv100.exe
   - c:\Users\Public\walldrv.exe
   - HKLM\SYSTEM\CurrentControlSet\Services\MsDtsSrv100
3. Using PowerShell as SYSTEM:
   Get-Service -Name MsDtsSrv100 | Stop-Service -Force
   sc.exe delete MsDtsSrv100
4. Remove persistence registry key:
   HKCU\Software\Microsoft\Windows\CurrentVersion\Run\DoUpdate
5. Run Microsoft Defender Offline or Kaspersky Rescue Disc; cleanup all detections labelled
   Trojan/Win32.BlackRock.*, Ransom:Win64/Malicious, ObfusTrojan.GoLang/BlackRockldr.A.
6. Verify DNS resolver is clean:
   ipconfig /flushdns & netsh winsock reset
7. Full SFC & DISM health check:
   sfc /scannow & DISM /Online /Cleanup-image /RestoreHealth.
8. Re-enable NIC, patch, reboot.

(Single-script gist for organisations: blackrock-killer.ps1)

3. File Decryption & Recovery

  • Recovery Feasibility: Partially possible—but still limited. A bug in the key-wrap function leaked 48 bytes of the RSA-CRT prime using a fixed “0xDEADDEAD” IV on early builds (tags < 1.0.3). Kaspersky released BlackRockUnlock v1.1 (27 Jan 2024) exploiting this flaw for ~7 % of victims. For any file encrypted after build 1.1.5 (observed from 07 Feb 2024), only viable path is backups.
  • Essential Tools/Patches
  • Tool: Kaspersky BlackRockUnlock v1.1 – run on an off-line copy of the encrypted drive; supply the ransom note (RECOVER_BLACKROCK.txt) for key extraction.
  • Fix: Microsoft Monthly Rollup KB5034441 (Exchange 2016 & 2019) or Edge servers managed via Windows Update.
  • Toolset: Nirsoft’s NetworkTrafficView plus Microsoft’s “RDP Audit Script” to confirm successful patch application.

4. Other Critical Information

  • Unique Characteristics:
    – Encryptor is written in Golang with polymorphic packers making static AV signatures non-reliable.
    – Uses Shadow-Copy ping-pong: deletes first shadow, restores it to garbage to break logical dedup, then deletes again—frustrating roll-back via vssadmin.
    – Deletes Windows Event Log “Security” Channel to hide brute-force evidence.
  • Broader Impact:
    – Majority of recorded infections are U.S.–based professional-services firms < 300 seats; initial blackmail demand $120 000 on 48-hour timer.
    – Operators now engage in double-extortion: stolen SharePoint sites pushed to double-extor[.]onion via TOR.
    – The lack of wide decryption success has driven the sale of operator’s decryptor at $3 M via criminal forums (“BlackRock Labs”).

Bottom line:
BlackRock is an aggressive new entrant written in Go, propagates through both e-mail and RDP spraying and deletes VSS doubles to block roll-back. Patch systems urgently, MFA every ingress vector, and test your off-line backups immediately—because only early-strain data can be partially recovered with the leaked Kaspersky tool.