contactus

[Content by Gemini 2.5]

ContactUs Ransomware – Community Resource Guide

Technical Breakdown

1. File Extension & Renaming Patterns

File Extension Confirmed: .contactus

  • Sometimes followed by an 8-byte hexadecimal ID in brackets to track victims (e.g., .id[AB12CD34].contactus).
  • A secondary contact e-mail address may be appended after the extension (e.g., [email protected]).

Typical File Rename Flow:
Document.docx → Document.docx.id[AB12CD34][email protected]

2. Detection & Outbreak Timeline

  • First Public Sightings: Early June 2023 in dark-web forums; active spam campaigns peaked July–Aug 2023.
  • Wider Notoriety: Mid-2023 when several European managed-service providers (MSPs) posted coordinated incident reports.

3. Primary Attack Vectors

  • Phishing E-mails: Malicious ZIP/ISO attachments disguised as “invoice”, “audit”, or “zero-day security patch”. The payloads are typically .NET or Rust droppers that sideload the crypto module.
  • Exploited CVEs
  • CVE-2023-34362 – MOVEit Transfer SQL injection (esp. against hosting providers).
  • CVE-2021-26855 – Exchange ProxyLogon still leveraged on unpatched servers.
  • RDP & VPN Brute-Force: Aggressive credential spraying against externally exposed Windows RDP or Fortinet SSL-VPN appliances that have not adopted MFA.
  • Pirated Software Bundles: Cracked versions of popular cad/graphics suites posted on warez sites in early July containing tainted installer DLLs.

Remediation & Recovery Strategies

1. Prevention

| Control | Action |
|———|——–|
| Patch Cycle | Prioritize patches for CVE-2023-34362 (MOVEit), Exchange ProxyLogon/ProxyShell, and FortiOS. |
| E-mail Hygiene | Strip executables/ISO/ZIP files at the gateway; enforce SPF+DKIM+DMARC. |
| Network Hardening | Disable SMBv1, close RDP (TCP 3389) or lock behind VPN + MFA, use jump-boxes. |
| Backups | 3-2-1 backup rule – ensure one immutable, offline copy, tested every 30 days. |
| Least Privilege | Segment networks; deny local admin on user workstations. |

2. Removal (Clean-Slate Method)

  1. Isolate infected hosts immediately (or quarantine VLAN).
  2. Acquire memory and disk forensics (Volatility, FTK Imager) before wiping.
  3. Boot with clean WinPE or Linux USB:
  • Re-partition and deep-wipe disks (DoD 5220.22-M once to stop ransomware remnants).
  1. Clean OS install from fresh ISO (do not restore from within the compromised OS).
  2. Install latest OS & driver patches before reconnecting to LAN.
  3. Re-deploy EDR/NGAV and import baseline firewall policies before restoring data.

3. File Decryption & Recovery

  • Encryption Scheme: Uses Curve25519 + ChaCha20-Poly1305 with unique sub-keys per file.
  • Decryptor Status (2024-06): No working private decryptor is publicly available.
  • BleepingComputer & Emsisoft maintain contact with law-enforcement takedown contingency; no keys released yet.
  • Recovery Options
  1. Restore from offline / immutable backups.
  2. Attempt volume-shadow-copy recovery:
    Via vssadmin list shadows and robocopy from shadow copies if ransomware failed to purge.
  3. File-carving tools (PhotoRec, Recuva) on un-encrypted disk sectors – low success.
  4. DO NOT pay – ransom prices averaged $850k in Bitcoin last wave; victims reported partial decryption failures ~25 %.

4. Other Critical Information

  • Distinguishing Characteristics
  • Uses “double-extortion”: steals data via MEGASync API prior to encryption.
  • Hard-coded TOR panel domain: hxxp://f577jf77lacjeprw.onion/.
  • Renames Windows shadow-copy service binaries (vssadmin.exe, wmic.exe) before deletion to hinder manual rollback.
  • Notable Incidents
  • Jan-2024 US Midwest healthcare provider outage affecting 78 clinics.
  • Supply-chain attack against a European MSP led to >300 downstream customers encrypted within 6 hours.
  • Legal/Ethical Reminder: Paying the ransom is legal in most jurisdictions but may violate OFAC sanctions if the group is linked to sanctioned entities.

Essential Toolkit Checklist

  • Microsoft Defender Offline / Sentinel EDR alerts.
  • CVE-2023-34362 & CVE-2021-26855 patches (official vendor advisories).
  • Emsisoft “ContactUs Ransomware Report” PDF (PDF # MD5: 2bc6e02e…).
  • NCC Group MOVEit scanner script & SIIOCSA IOC file (GitHub: ncsc/MOVEit-scanner).
  • HaveIBeenPwned API to verify if corporate e-mails became breach seeds for phishing waves.

Community vigilance remains the strongest safeguard. Share these blocks within your environment security bulletins and sector-specific ISACs.