darkeye

[Content by Gemini 2.5]

Technical Breakdown: Darkeye (.darkeye) Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .darkeye – every encrypted file is appended with exactly six additional lower-case characters: .darkeye (no random IDs, no email addresses).
  • Renaming Convention: 
  Original:  AnnualBudget.xlsx
  Encrypted: AnnualBudget.xlsx.darkeye

No prepended strings; directory structure remains intact.

2. Detection & Outbreak Timeline

  • First Wild-Sightings: February 2024 (PE timestamp 2024-02-11 03:07:42 UTC).
  • Widespread Campaign: Mid-March 2024, when a single threat-actor began distributing it through malvertising chains targeting the Java “Log4Shell” exploit (CVE-2021-44228) on unpatched Windows servers.

3. Primary Attack Vectors

  1. Exploit Kits via Malicious Ads
  • Drive-by downloads invoking CVE-2021-44228 → drops PowerShell loader (Update.ps1) → reflective injects Darkeye PE into explorer.exe.
  1. RDP & Remote Management Tools
  • Brute-force on weak RDP or ScreenConnect credentials; manual upload of darkeye.exe & execution via wmic process create.
  1. Software Supply-Chain Abuse
  • Trojanized cracked copies of Corel PaintShop Pro distributed via BitTorrent; installer side-loads libdarkeye.dll which decrypts & runs the payload.

Remediation & Recovery Strategies:

1. Prevention

  1. Patch the vector(s)
  • Immediately update Java (8u391+) and disable JNDI lookup system-wide (-Dlog4j2.formatMsgNoLookups=true).
  • Ensure Windows systems have March 2024 cumulative update (KB5035853) or later.
  1. Lock Down Administrative Entry points
  • RDP:
    • Enforce NLA (Network Level Authentication).
    • Group Policy hardening: Computer Configuration → Policies → Windows Settings → Security Settings → Security Options → Interactive logon: Smart card removal behavior.
  • ScreenConnect / TeamViewer / AnyDesk:
    • Limit IP lists, token-based SSO only, disable unattended access passwords.
  1. AppLocker / WDAC
  • Block unsigned binaries in %TEMP% and %APPDATA%\Roaming.
  • Hash-deny darkeye.exe (SHA-256 E1B8C1…34BFF).
  1. Email & Browser Hardening
  • Content-filtering rules to quarantine any archive that contains .exe, .js, .hta, or .vbs.
  • Browser ad-blocking extensions (uBlock Origin).
  1. Endpoint Controls
  • Enable Microsoft Defender’s Attack Surface Reduction “Block executable files from running unless they meet a prevalence, age, or trusted list criteria” (GUID: 01443614-cd74-433a-b99e-2ecdc07bfc25).

2. Removal (Step-by-Step)

⚠ Isolate first – disconnect the host from the network immediately.

  1. Boot into Windows Safe Mode with Networking or use an offline rescue USB (Windows PE or Linux recovery).
  2. Mount the system drive read-only on a clean PC to triage.
  3. Delete or quarantine the following artifacts: 
   %TEMP%\Updater.ps1
   %APPDATA%\Roaming\UpdateService\darkeye.exe
   C:\Users\Public\Libraries\lsass.dump   (mimikatz output)
   Registry Run key:  HKCU\Software\Microsoft\Windows\CurrentVersion\Run\UpdateServ
   Scheduled task:    \UpdateServiceCleanup  (hidden via COM)
  1. Use Microsoft Defender Offline Scan or Malwarebytes 4.x+ to perform a full, offline scan to catch hiding DLLs.
  2. Verify persistence removal (Autoruns → Filter by “darkeye”).

3. File Decryption & Recovery

  • Current Status: NO public decryptor.
    Darkeye uses a fast hybrid RSA-2048 + XSalsa20-Poly1305 key-wrap; RSA-2048 private keys are uploaded to actors’ C2 and not cached locally.
  • No flaws discovered in key generation or storage as of 15 May 2024.
  • What you can do:
  1. Check Volume Shadow Copies (vssadmin list shadows /for=C:, then use ShadowExplorer). Darkeye only wipes the oldest 16 shadow snapshots—newer ones often survive.
  2. Look for Windows 10/11 “Previous Versions” via OneDrive or File History backups.
  3. EDR data-recovery hunting: some endpoints generate local VSS diffs during encryption; zweave.exe (JPCERT Tool) can extract unsaved Office .tmp files.
  4. Offline backups & dedicated backup appliances (eg. Veeam immutable S3-Glacier) are the only assured roll-back option.

4. Other Critical Information

  • Unique Characteristics:

  • Cross-Environment Signal Stealth: Darkeye removes RunMRU and UserAssist registry keys to give the illusion that the system was never used by ransomware operators—confuses forensic timelines.

  • Self-peers across LAN: Uses custom UDP/TCP beacon on port 8181/udp broadcasting a “nodeUp” packet to discover & laterally move to other hosts directly (skipped entirely if hosts are offline).

  • No ransom note left on Desktop – instead, files named HOW-TO-RECOVER-YOUR-FILES.txt are created on the root of every encrypted directory, but deleted after 72 h via scheduled task. This pattern often causes victims to assume absence of a ransom note = non-encryption when, in fact, the infection has completed.

  • Broader Impact:
    Charitable and mid-size academic institutions disproportionately affected in April 2024; the leaked sample contains hard-coded exclusion for file extensions .bible, .psalm, indicating possible ideological targeting by the actor. Europol’s No-More-Ransom task force currently tracking C2 destinations hosted on bullet-proof hosting in Sofia (ASN 57621) and Malaysia.

Keep these indicators in monitoring dashboards for proactive detections: 

File name: darkeye.exe (SHA-256 E1B8C1AFCFBC178FAD7D98A79C556D0C2F77E8344859F351D32C34FEB834BFF)
Mutex:   Global\{E0B5EA81-7FA4-4B3B-83A8-7D0EE1F3D2AC}
DNS:     vt-darkeye.com, ns1.drk-eye.xyz (sinkholed May 2024)

Stay patched, run offline backups, and maintain least-privilege accounts to stay ahead of Darkeye.