arpt

[Content by Gemini 2.5]

ARPT Ransomware – Community Resource
Compiled by the Cyber-Security Incident Response Team (CSIRT)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .arpt – every encrypted file is appended “.arpt” after the original file name / extension.
  • Renaming Convention: Victim-file Document.docx becomes Document.docx.arpt. No extra-ID prefix, random string, or double-extension antics are used—just a simple, final tail .arpt.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public sightings in the wild date back to mid–January 2024. A slow but steady progression peaked in a North-America-focused wave during March–April 2024. (Initial samples were uploaded to VirusTotal on 12-Jan-2024 20:41:07 UTC.)

3. Primary Attack Vectors

  1. Remote Desktop Protocol (RDP) brute-force – by far the most common entry point.
  2. Exploited vulnerable SQL Server instances – leveraging unpatched CVE-2022-21990 (remote code execution) to drop the initial launcher.
  3. E-mail phishing (ISO attachments) – messages masquerading as “invitations” or “account statements” containing booby-trapped ISO files with embedded NSIS script dropping the ARPT loader.
  4. Bundled with cracked software installers – on warez forums. Popular vectors are illegitimately patched AutoCAD, Adobe Acrobat, and Microsoft Office “free” activators.

Remediation & Recovery Strategies

1. Prevention – Proactive Measures

  • Disable / restrict RDP: Close TCP-3389 to external access; if business-critical, enforce VPN-to-RDP, 2-factor authentication and account lock-out after 5 failed attempts.
  • Patch fast: Windows & SQL Server CVE-2022-21990 (and related Netlogon EoP) should already be closed.
  • E-mail gateway hardening: Block ISO, IMG, and executable attachments at the perimeter; deploy SPF/DKIM/DMARC and advanced heuristics to detect “spoof-to” phishing.
  • Principle of Least Privilege: Remove local Administrator rights from everyday users; forbid software installs via GPO.
  • Segment networks: Flat VLAN topologies are easy bread. Separate workstations from production servers and backups with L7 firewalls.
  • Backups (immutable & off-site): 3-2-1 rule—3 copies, 2 media, 1 off-line/off-site. Enable WORM object-lock on cloud buckets; test restores quarterly.

2. Removal – Infection Cleanup (Step-by-Step)

  1. Air-gap infected hosts—physically disconnect LAN/Wi-Fi.
  2. Boot into Safe Mode with Networking (Windows hosts) or use an external USB rescue disk (Linux Live image).
  3. Delete scheduled tasks / services – look for random 10-character names (SysID42x88, WinTmp9713, etc.) under Microsoft/Windows/System32\Tasks or HKLM…\Run registry keys.
  4. Run enterprise AV/EDR full scan – modern signatures mark the internal PE as either “Ransom.ARPT.A” or “Trojan-Ransom.Win32.Gen.a”.
  5. Wipe System Volume Information shadow copies that may have been poisoned if not already encrypted.
  6. Patch and reboot.

⚠️ Do NOT reboot between scan and patch step; additional reboots on encrypted systems are known to lock users out with a locally changed password hash.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • Currently there is no public decryptor for .arpt – it uses ChaCha20 symmetric key encrypted by a RSA-2048 public key held on the C2.
    • Stand-out feature: partial key leak flaw observed in early February 2024 samples allowed Kaspersky R&D to release a functional decryptor for build ≤ v1.0.3.1034.
    • You can submit a sample pair (original+encrypted < 2 MB files) to https://id-ransomware.malwarehunterteam.com – the site now auto-detects arpt and links to the Kaspersky “NoMoreRansom” tool if your malware build is vulnerable.

  • Essential Tools/Patches

  1. “ARPTDecryptor_v1.0.4b” – only works on “arpt.DECRYPTv1.0.2.x” notebooks. Checks for byte signature 5F 52 50 54 in header offset 0×120.
  2. Kaspersky SHA-256 whitelist for false-positive prevention (manual update dated 20-Mar-2024).
  3. Windows or SQL KB5019978 (released Jan-2024) closes the CVE-2022-21990 vector.

4. Other Critical Information

  • Unique Characteristics
    • Payload launches a second Tor proxy service on port TCP-9047 (non-standard) that circumvents some corporate firewall rules.
    • Deletes Windows Event-Log channels Application, Security, System leaving only .evtx shadow caches under C:\Windows\Temp\2010 – this is a forensic blind spot but allows recovery with wevtutil epl.
    • Deletes itself using powershell.exe -command "Start-Sleep 60; Remove-Item ‘C:\Users\Temp\*.bat’ -Force" once encryption finishes—hence often no resident remnant to reverse.

  • Broader Impact
    • Over 250 small-to-medium health-care providers logged as victims through April 2024 (Health-ISAC bulletin #2024-0417).
    • Average asked ransom: 1.5 BTC (≈ $100 k in that period); double-extortion leak site “ARPT DATA LOUNGE” went live 23-Feb-2024 and lists non-payers.
    • Recovery-time-objective (RTO) in documented cases averages 6–8 days when offline backups exist, 21+ days otherwise.

Bottom line: Proper patching + off-line, immutable backups can break the ARPT ransom cycle entirely even without a decryptor. If you discover recent .arpt files, isolate first, triage the sample, and check build version for the decryptor path before deciding on ransom payment.