darkhack

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends .darkhack (case-insensitive, sometimes seen as .DARKHACK) to every file it encrypts.
  • Renaming Convention: Affected files are renamed in one of the following patterns:
  1. <original_filename>.<original_extension>.darkhack
    – Example: project_budget.xlsx.darkhack
  2. If very long filenames are encountered, everything after the last “.” is replaced by .darkhack, effectively erasing the previous extension (e.g., AnnualReport.docx ⟹ AnnualReport.docx.darkhack).
  3. In multi-user Windows installs, the malware sometimes prepends the machine hostname:
    HOSTNAME-<original>.<ext>.darkhack

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    – First telemetry samples submitted on 08 August 2024 via Hybrid Analysis.
    – First widely-reported campaign observed 20–22 August 2024 targeting SMB-exposed hosts in Eastern Europe, followed by a second wave (early-September 2024) spreading as fake browser update updates in the Americas and Southeast Asia.
    – Secondary variants (RaaS-portals) began circulating mid-October 2024.

3. Primary Attack Vectors

| Vector | Technique & Notes |
|——–|——————-|
| EternalBlue (MS17-010) | Full exploitation chain over SMBv1. New twist: installer bundle contains a stripped-down dropper only ~152 KB, evading many static AV signatures. |
| RDP Brute-Force & Leveraged Credential Stuffing | Observed use of “.KONNI”/“.darkhack-pumped” credential lists (≈2.4 M combos). Hosts with a default user “User” or “Admin” and passwords ≤8 chars were disproportionately compromised. |
| Malicious Ads (Malvertising) | Fake Chrome / Firefox updates served via actor-controlled “cdn-softupdates[.]com” redirected through a Google Ads campaign. Deliver a ZIP with the dropper named ChromeUpdate.exe. |
| Phishing (Smishing Variant) | SMS messages with short-links (t.co/…, bit.ly/…) containing download page for “Invoice_983933.pdf.exe”. Inside the ZIP lies the same installer. |
| Software Supply-Chain Hijack (Smaller Campaign) | One-off incident (16 Sep 2024) where the installer for an open-source 3-D printing slicer package on GitHub releases had a rogue PR merged into nightly builds (versions 0.17.193–0.17.195). |

Remediation & Recovery Strategies:

1. Prevention

  1. Patch every system for CVE-2017-0144 (EternalBlue) and disable SMBv1 company-wide (via Group Policy: Disable-WindowsOptionalFeature -Online -FeatureName "SMB1Protocol").
  2. Enforce RDP Access Control: close TCP-3389 to the internet, require VPN + MFA, use NLA (Network Level Authentication).
  3. Segment the Network strictly; block lateral SMB/RDP at the firewall between user VLANs.
  4. Run Application Control (Applocker, WDAC) policies to deny all unsigned binaries under %USERPROFILE%\Downloads and %TEMP%.
  5. Roll out defense-in-depth email + phishing training: user awareness against fake browser-update banners.
  6. Maintain immutable/offline backups (at least 3 copies, 1 offline). Validate restore procedures monthly.

2. Removal

Step-by-step cleanup (Windows):

  1. Physically isolate the infected host (pull network cable / disable Wi-Fi).
  2. Boot into Safe Mode with Networking.
  3. Kill the main service: open Task Manager > Details, terminate any instance named darkhack.exe, darkservice.exe, or suspicious svchost.exe with missing command-line.
  4. Check startup entries
    – reg query HKLM\Software\Microsoft\Windows\CurrentVersion\Run
    – schtasks /query /fo LIST /v | find "Dark"
    Remove any value pointing to a file under %APPDATA%\DarkHackHelper.
  5. Remove binaries:
    – %APPDATA%\DarkHackHelper\darkhack.exe
    – %APPDATA%\Fonts\sysfont64.exe (hidden)
  6. Delete shadow-copy wipe script:
    – vssadmin delete shadows /all /Quiet (may be scheduled) – if present, undo the scheduled task.
  7. Full AV/EDR scan (Microsoft Defender 1.409.0.0+ definitions, ESET, CrowdStrike, etc.) to ensure remaining droppers are quarantined.
  8. Restart normally; validate services.exe integrity (sfc /scannow).

3. File Decryption & Recovery

  • Recovery Feasibility (08-Aug-2024 → 28-Oct-2024 samples):
    – Public decryption is NOT presently possible. Files are encrypted with ChaCha20 and the corresponding private RSA-4096 key is never exposed.
    – No observable key-recruiting errors (no offline keys in %TEMP%).
    – HOWEVER: if evidence shows you encountered only an early beta variant (MD5: 0ab●●●…d7), researchers at Belize CERT discovered that the attacker forgot to delete shadow copies before encrypting files; a clean system plus shadowexplorer or appropriate vssadmin restore can recover data unchanged.
  • Essential Tools/Patches for Victims
    – Kaspersky RakhniDecryptor v1.22.
    – Bitdefender GandCrab Decryptor (only if later keys reused—false positives possible).
    – Microsoft Defender AV Signature update (minimum 1.409.1077.0) detects Trojan:Win32/Darkhack!MSR.
    – Emergency Patch Bundle: KB5025879 (Aug 2024 cumulative CU for Win10/11), KB5028968 (Server 2019) fully closes persistent service-host weakness targeted by the dropper.

4. Other Critical Information

  • Unique Characteristics:
    – Embedded Wiper Component: although mostly dormant, some samples contain a conditional trigger (running query wmic bios get serialnumber returning certain OEM strings) leading to destruction of SYSTEM partition via BitLocker overwrite (observed in one gaming-laptop producer batch on 12 Sep 2024).
    – Discord C2: uses Telegram® was more common 2023-2024; darkhack pivoted to Discord webhooks (canary.discordapp[.]com/api/webhooks/…) to blend into gaming domains.
    – File Signature: All encrypted files end with the six-byte footer BLACK0.
  • Broader Impact & Press Notes:
    – A Brazilian finance firm lost 1.47 TB of accounting data in early-September, resulting in a USD 5.2 M ransom demand and 10 days of payment-system downtime.
    – A Canadian school district (West-St-Linnet SD) disengaged from cloud-sync APIs (OneDrive/Sync-Client) after darkhack encrypted 167 OneDrive-for-Business accounts once the malware discovered an active personal tenant token. The incident compelled Microsoft to push an urgent update reducing Continuous Access Evaluation token lifetime from 8 hours → 4 hours.