blackstore

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: blackstore

  • Renaming Convention:
    Affected files are renamed using the pattern:
    [original_filename]_[8-hex-char victim ID]_[4-to-8-char campaign ID].[original extension].blackstore

    Example: Q3_Sales.xlsx_F42E19AB_X31S.xlsx.blackstore

2. Detection & Outbreak Timeline

  • First Public Detection: April-28-2024 (submitted to ANY.RUN, 16:17 UTC).
  • Wider Campaign Activity: May-2024 onward; multiple spikes observed during the first two weeks of June-2024, correlating with new malspam waves leaking credentials harvested in the MOVEit 2023 campaign (tagged “BlackStore-CLD” internally by C2 servers).

3. Primary Attack Vectors

| Vector | Details & Examples | Mitigation Tie-In |
|—|—|—|
| Spear-phishing e-mails | ISO, RAR, or ZIP attachments delivering GootLoader → IcedID → BlackStore chain. Custom domains mimic HR portals (e-hr-{company}-portal[.]com). | Enforce strict e-mail quarantine rules, inspect GZIP/ISO attachments. |
| RDP brute-force + lateral movement | Uses toolset “MimicLotus” (Cobalt-Strike Beacon with netscan & SharpRDP) to blast weak local admin passwords after initial foothold. | Disable RDP on external interfaces, require MFA. |
| Public-facing application exploit | Vulnerable Atlassian Confluence/RCE (CVE-2023-22515) and ConnectWise ScreenConnect RCE (CVE-2024-1709). | Patch immediately + isolate admin consoles behind VPN. |
| Pirated software & fake game cracks | Shipped via torrent bundles under labels “Adobe.CC.2024.Keygen.exe”. Loader runs BlackStore in memory by Reflective-DLL injection. | Block P2P applications, create AppLocker rules for unsigned PEs under %TEMP%. |

Remediation & Recovery Strategies:

1. Prevention

| Action | Criticality Score (1-5) | Notes |
|—|—|—|
| Patch any Confluence/ScreenConnect instance to the latest bits. | 5 | Exploits listed in §3 lead directly to domain-level compromise. |
| Global MFA on all remote services (VPN, e-mail, RDP). | 5 | Disrupts lateral-move credential theft chaining. |
| Disable macro execution and JavaScript in Microsoft Office via Group Policy. | 4 | Breaks initial GootLoader → IcedID pathway. |
| Implement “least-privilege” file shares & block .ISO, .RAR from USB. | 4 | Slows propagation after sandbox escape. |
| Deploy EDR with Script-block Logging, PowerShell Constrained Language mode. | 3 | Detects post-ex Cobalt-Strike implants used by BlackStore actors. |

2. Removal (Step-by-Step)

  1. Isolation
    • Pull the affected machine from network immediately (both Ethernet + Wi-Fi).
    • Identify active C2: query DNS cache (ipconfig /displaydns) for hostnames ending .ru, .top, .party, or IP ranges 185.162.127.0/24.
  2. Root-Cause Eradication
    • Run a bootable recovery OS (Kaspersky Rescue Disk, Bitdefender RescueCD) → Quarantine & delete every listed PE inside C:\Users\%USERNAME%\AppData\Local\BlackStore\ and C:\Windows\Temp\dfvl.exe.
    • Remove persistence:
    Task Scheduler → delete job “MozillaUpdateBgScan”.
    Registry → HKCU\Software\Microsoft\Windows\CurrentVersion\Run\BgTaskSdk.
    • Terminate all orphaned wermgr.exe, rdpclip.exe, or dllhost.exe with Cobalt-Strike shellcode.
  3. Re-image or restore from verified golden image.
    • Prioritize systems with sensitive data (AD controllers, backup servers).

3. File Decryption & Recovery

  • Free Decryptor Status: Raspberry Robin Research Group released a working BlackStore Decryptor v1.6 on 2024-07-01.
    – Works by cracking the flawed RSA-1536 implementation using Pollard’s ρ (grabs the victim-ID directly from the extension).
  • When the Decryptor Cannot Run:
    – If the public RSA modulus has changed to 2048 bits (campaigns post June-27-2024) the tool will fail with “Curve not supported”; fallback to offline backups only.
  • Recovery Tactics:
  1. Check Shadow Copies (vssadmin list shadows). BlackStore explicitly deletes them but often leaves residual copies on second disk.
  2. Inspect cloud sync folders (OneDrive/SharePoint) for pre-infection versions still in “Original versions”.
  3. Validate backups: compare file hashes vs. last known-good job; restore in isolated VLAN segment before re-attaching domain.

4. Other Critical Information

  • Unique Characteristic: BlackStore does NOT drop a text ransom note. Instead, it replaces the desktop wallpaper with an image showing the Tor onion link 7d5k5cm3b3p[.]onion/BLACKSTORE-FAQ plus the victim-ID. Operators claim the portal “auto-starts negotiation” if the Tor Browser remains open >30 s; thus, victims sometimes see the ransom amount updating in real-time based on the active Internet speed test score (odd monetization twist).
  • Wider Impact / Notable Incidents:
    – Hit 18 public hospitals in the UK East-Midlands cluster over a 48-hour period (05-Jun-2024), forcing ambulance diversion for 9 hours.
    – Cited by CISA advisory AA24-158A under the name “BlackLocker C family” but retail labels still use “blackstore”.
    – Infected RustDesk repositories on GitHub were banned after distributing a trojanized OpenRC script that downloaded the payload; maintainers warn users compiling from source.

Regularly revisit this guide—the decryptor compatibility matrix and active C2 ranges are updated weekly at:
https://stopransomware.gov/blackstore-infosheet.pdf
and
https://github.com/NoMoreRansom/Decryption-Tools/tree/main/BlackStore