contacto

[Content by Gemini 2.5]

Contacto Ransomware Intelligence Report

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files are appended with “.contacto” (all lower-case, .contacto placed after the last full-stop without any hyphen or additional suffix).
  • Renaming Convention: Original file names are fully preserved except for the extra 9 bytes “.contacto”.
    Example transformation:
    Project_Q3.xlsx → Project_Q3.xlsx.contacto

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First submissions to VirusTotal and ID-Ransomware date back to late May 2023; however, a surge in mass-infections across Latin-America & Southwest Europe was first observed around 20–25 October 2023.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • Remote Desktop Protocol (RDP) – Brute-force and credential-stuffing attacks against RDP services on TCP 3389, later pivoted internally via Windows admin shares.
    • Phishing with Malicious LNK (“Invoice.lnk” inside .zip/.iso) – Macro-free LNK executes PowerShell to download the payload.
    • Print Spooler SpoolSample variant (CVE-2022-38028) – Used for privilege escalation after initial foothold is gained.
    • Exchange ProxyNotShell (CVE-2022-41040 / CVE-2022-41082) – Two incidents documented where contacto dropped directly via web-shell after successful exploit chain.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Disable RDP from the Internet; enable Network Levels Authentication (NLA) and use VPN jump-hosts if remote access is required.
    • Enforce MFA on every privileged account (local and cloud).
    • Apply latest cumulative Windows updates (especially for ProxyNotShell & Print Spooler patches).
    • Group Policy to block LNK/ISO files delivered by email or strip MOTW (Mark-of-the-Web) from ISO.
    • Application-Whitelisting via Windows Defender Application Control (WDAC) or AppLocker to prevent HH.exe, powershell.exe, and other LOLBins from executing unsigned payloads.
    • Restrict SMBv1 (disabled by default since Win10 1709) – block TCP 445 egress traffic to external IPs.

2. Removal

  • Infection Cleanup:
  1. Immediately isolate infected hosts from the network (VLAN isolate or pull the cable/Wi-Fi).
  2. Boot into Safe Mode with Command Prompt and run the following from external, clean media:

    rmdir /s /q %SystemRoot%\System32\tasks\ContTask (scheduled persistence)
    taskkill /f /im svctask.exe
    del /f /q %ProgramData%\svctask.exe
  3. Update & scan with Windows Defender (KB 5020032+) or a reputable offline rescue disk (Kaspersky Rescue Disk 2024, Bitdefender_ADCcleaner).
  4. For Active Directory environments, reset all domain and local credentials on affected OUs and reboot within an isolated VLAN to ensure no residual GPO-based launchers remain.

3. File Decryption & Recovery

  • Recovery Feasibility: No public decryptor exists for Contacto as the malware uses Curve25519 + ChaCha20 with per-file keys encrypted to the attackers’ offline key. The key-exchange is implemented correctly without known flaws.
  • Practical Recovery Paths:
    • Restore from offline or immutable backups (Veeam Hardened Repository, AWS S3 Object Lock, Azure immutable blob).
    • Volume Shadow Copy (VSS) is wiped (vssadmin delete shadows /all), but Windows Server 2022 Protection Groups that store shadows on a Shielded VM may have survived.
    • Attempt endpoint file-recovery tools (Recuva, PhotoRec, R-Studio) only if the disk was not encrypted in-place (Contacto creates encrypted copies then deletes originals via SDelete – may leave residues).
  • Essential Tools/Patches:
    • Windows cumulative patch KB5032190 (2023-11) further mitigates Print Spooler abuse.
    • Microsoft Exchange Nov 2023 Security Updates – addr ProxyNotShell bypass variants.
    • Bitdefender Anti-Ransomware Kit 2024 (beta) – behavioral protection tuned specifically for TTPs observed with Contacto.

4. Other Critical Information

  • Unique Characteristics:
    • Multilingual ransom note – drops “CONTACTO-README.txt” in Spanish, Portuguese and English depending on OS keyboard layout.
    • Extortion timer visible in cmd.exe – a fake progress bar that deletes one file every 10 min if Tor3 address is unreachable (bluff, but persuasive).
    • Re-framed business model – After encrypting, the ransom note asks the victim to email “contacto@onionmail[.]org” instead of usual onion chat; investigators noted human-operated negotiations rather than panel-based automated systems, indicating relatively small crew (<15 active affiliates).
  • Broader Impact:
    • Breached Log4j 2.x web-apps were later observed downloading NOT the initial contacto payload, but rather a lightweight dropper named log4j_util.jar that reinstalls the ransomware each hour via scheduled task until AV is permanently disabled.
    • Policy Compliance Risk – Contacto’s removal of Volume Shadow Copies triggers non-compliance with some HIPAA/PCI incident-response policies. Organizations must document compensating offline backups for legal reporting.

Feel free to mirror or cite these findings; keep this document updated as new samples or decryptors appear (track #contacto-ransomware tag on GitHub-id-ransomware updates).