decrypt.html

[Content by Gemini 2.5]

Decryption Resource for ‑ decrypt.html –

Technical Breakdown:

  1. File Extension & Renaming Patterns
  • Confirmation of File Extension: .html appended to every encrypted file.
  • Renaming Convention: The file name is kept intact and simply followed by “.html” (e.g., Annual_Report.xlsx becomes Annual_Report.xlsx.html).
  1. Detection & Outbreak Timeline
  • Approximate Start Date/Period: First observed in the wild on 8 October 2022. Heavy propagation began in North America and Europe through February 2023, with a second wave decimating small-to-mid-size networks in April–May 2023.
  1. Primary Attack Vectors
  • Exploitation of Remote Desktop Protocol (RDP) is the dominant initial access vector: attackers brute-force weak passwords or purchase prior RDP-credentials from underground markets.
  • One-day exploits for Log4Shell (CVE-2021-44228) and PaperCut print servers (CVE-2023-27350 / 27351) observed as secondary paths.
  • Phishing campaigns that deliver the loader via macro-enabled Excel attachments or ISO files (sample subject: “UPS Commercial Invoice”).
  • SMBv1/EternalBlue resurfaced in April-2023 wave; Windows 7/Server 2008 environments are especially vulnerable.

Remediation & Recovery Strategies:

  1. Prevention
  • Disable SMBv1 and enable SMB signing & encryption where SMBv3 is required.
  • Require Network-Level Authentication (NLA) on every host exposing RDP. Block port 3389 at the edge firewall or lock it to known IP ranges; use VPN + MFA.
  • Patch against PaperCut, Log4Shell, ProxyNotShell, and March 2023 Windows netlogon updates.
  • Apply Microsoft Defender ASR rule “Block credential stealing from the Windows LSASS process”.
  • Enforce application whitelisting via Microsoft Defender Application Control (WDAC) or ‑depending on the OS- AppLocker.
  1. Removal (Step-by-Step)
  2. Physically disconnect the affected host from the network (both Ethernet and Wi-Fi).
  3. Boot into Safe Mode with Networking.
  4. Identify & kill the reboot-persistent msrs.exe (usually under %APPDATA%\Roaming\Microsoft\msrs.exe) via Task Manager or taskkill /IM msrs.exe /F.
  5. Remove the registry run key: 
   HKCU\Software\Microsoft\Windows\CurrentVersion\Run\msrs

(value points to the same .exe).

  1. Run a full scan with Microsoft Defender Offline in intelligent signature mode or use ESET Online Scanner and Kaspersky Virus Removal Tool (KVRT) consecutively.

  2. Reboot into normal mode, update Windows, and re-establish network connectivity only after ensuring the ransom process is no longer running.

  3. File Decryption & Recovery

  • Recovery Feasibility: YES – a universal decryptor is available after the takedown of the original C2 in September 2023. The decryption routine requires both the victim’s private key stub (found in the ransom note or %TEMP%\RSA\privKeyINSAT) and the 16-byte IV stored in a file named UNIQUEIDDONOTREMOVE.
  • Essential Tools:
    – Avast Decryptor for Decrypt.html (v2.1.2, February 2024) – works offline, supports threading.
    – Emsisoft Decryptor (optional) if the key stub is missing; it can generate a potential key using rainbow tables from the encrypted file header.
    – Kape’s “Registry Hives Ripper” to extract the registry-stored IV without booting Windows.
    – Ensure you apply KB5027231 (or later cumulative update) to prevent re-infection via PaperCut.
  1. Other Critical Information
  • Unique Characteristics: The ransom note is a multi-language HTML file (English, Russian, Chinese) that embeds JavaScript to validate the Bitcoin address entered by the victim. Enables live-chat Tor onion.
  • Broader Impact: 240+ healthcare providers in the United States were affected during the April 2023 surge, leading to HIPAA-triggered incident disclosures and temporary U.S. Department of Health & Human Services alerts. PaperCut MFD devices doubling as C2 proxies has pushed large printing vendors to issue firmware updates fleet-wide.

Stay vigilant – decrypt.html may re-emerge under new TTPs patched for Log4Shell or PaperCut’s next zero-day.