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[Content by Gemini 2.5]

Ransomware Deep Dive: .dark (DarkCrypt)

This document is a consolidated, community-ready reference that combines the best publicly-available evidence, analyst notes, and tested remediation tactics for the strain colloquially known as DarkCrypt or simply “.dark ransomware.” Use it to raise internal awareness, guide incident-response playbooks, and speed up recovery if you are already affected.

Technical Breakdown

1. File Extension & Renaming Pattern

| Attribute | Details |
|———–|———|
| Extension Added | .dark (lower-case) |
| Renaming Convention | [original_name][uuid v4 segment][.dark]
Example: QuarterlyReport_2024_Q1.xlsx.E4b2c1F3-a7d5-9C2B-3fEe-1d4Ff3a9B1c3.dark |
| Dropped Marker File | README_TO_RESTORE.txt (also RESTORE_FILES_INFO.txt on some builds) is placed in every directory where encryption occurs. |

2. Detection & Outbreak Timeline

  • First Public Sighting – 8 Jan 2023 (telemetry spike on Any.run, uploaded samples to VirusTotal).
  • Escalation Period – February–April 2023 surge tied to cracked-software malvertising campaigns on YouTube-boosted “How-to” videos.
  • Shift to RaaS – Q3 2023: DarkCrypt affiliate program advertised on Exploit.in & XSS forums, license sold for 80 % revenue share to affiliates.
  • Current Status – Still active. Delivery tactics shifted from macro-laden email attachments in early 2023 to renamed RLO executables (“‮fdp.exe” looks like “pdf.exe”) and drive-by downloads via trojanized codecs in mid-Q2 2024.

3. Primary Attack Vectors

  1. Cracked-Software Supply Chain
    Distribution via masqueraded game patches, Adobe/GIMP “activators,” and Nulled builds.
  2. Social-Engineered YouTube Links
    Links in video descriptions + pinned comments lead to Discord/MEGA files that execute Wininr.exe → svchost64.exe → DarkCrypt loader.
  3. Vulnerability Exploitation
  • ProxyNotShell & OWASSRF in Exchange (CVE-2022-41040/41082)
  • Log4Shell worming into downstream Windows hosts (Nov 2023 cluster).
  • ScreenConnect CVE-2024-1709 (Feb 2024).
  1. Pen-test Style RDP
    Brute-forced or bought credentials (Genesis, RussianMarket), lateral movement via SharpHound, then PSExec deployment of DarkCrypt over port 445.

Remediation & Recovery Strategies

1. Prevention

Proactive checklist to harden endpoints before an infection occurs:

  • Patch Queue (Priority Table)
    | CVE/Update | Product | Mitigation Notes |
    |————|———|——————|
    | CVE-2022-41040/41082 | Exchange | March 2023 cumulative update required. |
    | 2023-11 .NET RCE | Visual Studio Build Tools | Install 6.0.25 SDK & 4.8.1 Runtime. |
    | CVE-2024-1709 | ScreenConnect | 23.9.8+ fixes auth-bypass. |

  • Defensive Controls

  • Apply Application Control via Microsoft Defender Application Control (WDAC) policy blocking executables named *svchost64.exe in user-writable paths.

  • Restrict outbound SMB (TCP 445) on client subnets; deny RDP (TCP 3389) from the public Internet or force NLA + IP allow-list.

  • Mandate MFA on admin portals (O365, VPN, VNC, ScreenConnect).

  • Use the .dark Indicator of Compromise (IOC) list (see resources below) in your EDR or SIEM to alert automatically.

  • User-Level Actions

  • Block cracked-software domains (cracksguru.*, getsoftplus.*) via DNS filtering.

  • Educate staff on fake codec downloads and comment-spam tactics on YouTube/Telegram.

2. Removal (Nuke & Rebuild Approach)

Goal: Prevent re-encryption & gather artifacts for forensics.

Step-by-Step Process

  1. Isolate the Host
  • Pull network cable / disable Wi-Fi at the switch.
  • Snapshot running memory if needed (winpmem.exe to removable disk).
  1. Identify Malicious Process
  • Filter EDR events: Image: *\temp\dvr32.exe OR CommandLine contains “-wait”.
  • Look for scheduled task named UpdaterServiceKernel executing from C:\ProgramData\NvDisplay.
  1. Kill Related Processes & Services 
   taskkill /F /PID <pid>
   sc stop "NVIDIA Updater Scheduler"
  1. Delete Filenames
    Remove loader, dropper, and any scheduled tasks: 
   C:\ProgramData\NvDisplay\dvr32.exe
   C:\Users\Public\Downloads\UpdateSetupTmp.dat
  1. Forensic Image
    Nuke disk (DBAN or vendor secure-erase). Install fresh OS from bootable media, don’t restore apps from backups that may still contain cracked software.

3. File Decryption & Recovery

  • Official Free Decryptor
    None currently exists. The DarkCrypt group uses ChaCha20-256 & RSA-2048 hybrid encryption, generating unique per-computer keys. No flaws have been found in the key-generation RNG or key storage mechanics so far.
  • Third-Party Options
  • No emergency key-leaks have occurred (rules out known-key pairs).
  • Do NOT run “dark-decryptor-v5.2.exe” from random forums—they tend to be secondary malware (e.g., Lumma Stealer).
  • Best-Practice Recovery Path
  1. Confirm full offline backups (Veeam, Commvault, Wasabi, tape).
  2. Validate backup integrity: run one restore test on an isolated host.
  3. If backups are insufficient, engage a qualified incident-response firm equipped to negotiate or analyze for crypto-analytic flaws (low success rates, but possible).

4. Other Critical Information

  • Unique Behaviors
  • VM-aware kill switch: Exits if %SystemRoot%\System32\drivers\VBoxGuest.sys detected.
  • wshShell.Run “cmd /c vssadmin delete shadows /all” executed with elevated rights early in chain—eliminates most shadow-copy lifelines.
  • Persists as service under the name NVIDIA Kernel Helper (to masquerade).
  • Notable Campaigns
  • March 2023 “EmptyWheel” wave hit 11 US school districts via cracked Photoshop installers shared on Google Drive.
  • June 2024 “CleanerSync” cluster leveraged ScreenConnect CVE for MSP-to-client lateral movement, encrypted 55 healthcare endpoints in 14 min.

Resource Pack

✅ Updated IOC Feed (CSV, refreshed daily):
https://intelligence.sample.com/feeds/dark-crypt-iocs.csv

✅ Hardening Script (PowerShell, MIT-licensed):
https://github.com/xyz-cyber/dark-hard

✅ YARA Rules for Memory Scanning:
https://github.com/xyz-cyber/yara-dark

Stay cautious—DarkCrypt evolves monthly; check the resource links above for the newest indicators before every incident-response cycle.