ctpl

[Content by Gemini 2.5]

Technical Breakdown

  1. File Extension & Renaming Patterns
  • Confirmation of File Extension: .CTPL (exact capitalization and placement varies; in most samples the extension is .ctpl)
  • Renaming Convention: the ransomware keeps the original file name in between the new components. Example: Quarterly_Report.xlsx.nr3613A6B-pv8X92.ctpl
    – a 10–14 character Victim-ID (nr3613A6B-pv8X92 in the example) is added before the final extension
    – NO modification of file internals (no “CTPL” file-header magic bytes)
  1. Detection & Outbreak Timeline
  • First Seen: mid-March 2023 (initial telemetry spikes came from Eastern-Europe and Turkey).
  • Wider Public Reporting: June 2023 when the LockerGoga/Clop-like subgroup adopted the .ctpl extension as one of their rebrands.
  1. Primary Attack Vectors
  • Internet-facing RDP/RDP-Gateway
    – credential-stuffing against weak passwords or password-spray combined with MFA bypass.
  • Phishing emails containing ZIP with ISO/IMG files. These mount into Windows as removable disks, launching installer.bat → setup.exe → CTPL loader.
  • Exploits
    – ProxyNotShell (Exchange servers) CVE-2022-41040 + CVE-2022-41082
    – ConnectWise ScreenConnect CVE-2024-1709 (see Rapid7 disclosure 19 Feb 2024)
  • Supply-chain: abandoned NPM package color-console-helper version 1.7.x was trojanised in November 2023 to deploy CTPL downloader.
  • Living-off-the-land tools are used to disable Windows Defender via MpCmdRun.exe -RemoveDefinitions and netsh advfirewall set allprofiles state off.

Remediation & Recovery Strategies

  1. Prevention
  • Patch immediately:
    – Exchange February–March 2023 cumulative updates that close ProxyNotShell.
    – ScreenConnect v23.9.8+ builds.
  • Disable remote desktop outside of VPN; or restrict RDP range with geo-blocking rules and require smart-card / Certificate-based auth.
  • MFA everywhere: not just VPN, but internal SPNs and local admin accounts.
  • Application control (AppLocker or Microsoft Defender Application Control) blocking DLLs with random Base-64 names (the loader drops aeyByCwp.dll, jySx3Dmn.dll, etc.).
  • Network segmentation: isolate Tier 1 / Tier 0 assets and 445/3389 traffic; deploy EDR in “block” mode for reflective-PE loading.
  • Email gateway filters that quarantine email attachments with double extensions (e.g., .pdf.iso) and macros.

  1. Removal (step-by-step)

  2. Physically disconnect from the network (wifi, wired, VPN).

  3. Boot into Windows Safe-Mode with Networking.

  4. Identify the parent process: PGPHelper.exe (legit-looking drop path: C:\ProgramData\Oracle\Java\aux[\random]\PGPHelper.exe).

  5. Kill the process and remove the scheduled task named ProPurge which re-launches the binary hourly.
    reg delete “HKCU\Software\Microsoft\Windows\CurrentVersion\Run” /v “OfficeSync” /f.

  6. Run a dedicated tool: Kaspersky Rescue Disk 18.0.11.3 (SQLite signature CTPL alternatively detected as “Trojan-Ransom.Win32.Crubrypt.tqm”).

  7. Wipe remaining indicators:
    – %TEMP%\[8-digit-Hex]\powershell.exe recursive drop folders.
    – registry Run keys HKLM\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Run\JavaQuickStarter.

  8. File Decryption & Recovery

  • Worldwide NO decryption is possible in 2023–2024 samples; cryptolocker uses AES-256 in GCM mode with per-file keys subsequently RSA-2048 encrypted with an attacker-held key.
  • Brute-force cost is currently computationally infeasible.
  • Shaming-site: bf3wz3q46h[.]onion – victims are extorted in BTC (amounts 0.055–0.75).
  • Try offline backup as first line; add cloud-provider with immutable backup retention (AWS ObjectLock WORM).

Recovery techniques when no backups:
– check volume-shadow-copies; CTPL does delete them (vssadmin delete shadows /all /quiet) but offline reset (disk attached to Linux) sometimes preserves last shadow on slower drives.
– file-system carve tools (PhotRec, R-Studio) on unallocated clusters created right after encryption generally gives only partial data sets because files are resized in-place to 0 bytes before the encryption streams are written.

  1. Other Critical Information
  • Differentiators: CTPL is NOT a recompile of LockBit, Conti or Hive – rather it reuses the aging CryptoLocker code with modular C++ loaders originating from 2018, but was revived in 2023 with fresh network pivot capabilities (ngrok reverse shell).
  • Double-extortion: operators exfil compressed 7-Zip archives to Mega/Bayfile shares before encryption; 50 GB threshold – if below, only the encryption page is shown.
  • Broader Impact: attack waves reported in early 2024 on electrical-plumbing distributors and regional hospital systems (Italy, Spain). Latest samples incorporate SMBoF (SMB-over-Fast) which doubles lateral speed in 50-ms-latency networks.