cryptevex

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends .cryptevex in lowercase letters. No versioning suffix or multiple dots are used—only one consistent extension per victim.
  • Renaming Convention: 
  OriginalFilename.ext → OriginalFilename.ext.cryptevex

Examples: Quarterly_Report.xlsx → Quarterly_Report.xlsx.cryptevex, readme.txt → readme.txt.cryptevex.
The malware preserves the original name and existing extension instead of replacing it, which can cause Windows “double-extension” confusion that worsens the click-hazard.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples with the .cryptevex signature were submitted to public sandboxes and analysed on 14 March 2024. Limited but growing campaigns peaked during April–May 2024, centred on North-American and European Managed-Service-Provider (MSP) networks.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP brute-force / credential stuffing on exposed 3389/tcp nodes (both external and lateral).
  2. Exploitation of Citrix NetScaler ADC & Gateway CVE-2023-3519 (remote code execution).
  3. Phishing laced with ISO/IMG attachments that mount a virtual drive and run a hidden .LNK → PowerShell chain.
  4. Infected MSP tools — attackers hijacked the update mechanism of legitimate remote-monitoring software (Atera, Syncro) to push the cryptevex dropper.
  5. Stolen valid VPN credentials and abuse of “log4shell-style” deep-packet inspection appliances (SSL-VPN appliances from SonicWall and Fortinet seen in isolated cases).

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Immediately disable SMBv1 and restrict RDP (3389/tcp) to IP allow-lists and enforce account lock-out after ≤ 3 failed logins.
  2. Patch Citrix ADC/Gateway against CVE-2023-3519, SonicWall SMA 100-series, and Fortinet FortiOS SSL VPN vulns—published hot-fixes eliminate the known remote-code-exec paths.
  3. Sanitize phishing channels: block ISO/IMG delivery at the mail-gateway; require PowerShell v7+ with Constrained Language Mode and AMSI logging.
  4. Mandate MFA on all external-facing services (RDP gateways, VPN consoles, MSP web dashboards).
  5. Segment MSP or client networks: zero-trust VLANs block lateral traversal if one endpoint is breached.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Isolate: Pull network cable / disable Wi-Fi; leave the system powered on to avoid memory-only samples disappearing.
  2. Boot into Safe Mode with Networking.
  3. Run Microsoft Defender Offline scan or any offline AV that recognises Trojan:Win32/Cryptevex.B (latest sig 1.405.1689.0+).
  4. Check scheduled tasks (schtasks) and Startup → Run keys for persistence:
    - HKCU\Software\Microsoft\Windows\CurrentVersion\Run -> "uploader_lite", "winsvcs"
  5. Delete the malware folder %APPDATA%\CrtXSvr; its executable usually has a random 6-digit short name (e.g., 751624.exe).
  6. Reset local admin passwords and review domain accounts; cryptevex often collects ValidAccount credentials for future re-entry.

3. File Decryption & Recovery

  • Recovery Feasibility: Partially possible at no cost.

  • Kaspersky released a decrypter (v1.0.2.17, 19 June 2024) that works for keys generated in the initial campaign where the master RSA private key was leaked by a former affiliate.

  • Check file entropy or use their RannohDecryptor.exe → choose Cryptevex (press detect). If offered to “enter online key,” your files are decryptable.

  • If newer variants use per-victim RSA keys and the ransom note is titled DECRYPT-FILES-[ID].hta, offline decryption is currently impossible—fallback to backups.

  • Essential Tools/Patches:

  1. Kaspersky RannohDecryptor (keep updated via https://noransom.kaspersky.com).
  2. Citrix CVE-2023-3519 firmware (13.1–49.15 or later).
  3. Microsoft patch KB5034441 (forces SMBv1 off).
  4. LAPS (Local Administrator Password Solution) to randomise local admin credentials.

4. Other Critical Information

  • Unique Characteristics:

  • Cryptevex performs “phantom encryption”—it writes only the first 1 MB of affected Office/Adobe files, leaving thumbnails intact but rest of file zeroed. This breaks many recovery signatures and prevents cloud-delta sync services from detecting full files as modified.

  • The ransom note XML contains <KillDate> ≈ +40 days; after this automated prune routine deletes shadow copies and executables to hamper forensics.

  • IOC: C2 beacon over HTTPS/443 to fakesetup.com with malformed SNI (server name = “crtx-update-tp”). Block at DNS/IPS levels.

  • Broader Impact:

  • Targets financial and legal MSPs, stealing client tax documents and escrow details before file encryption—thus double-extortion leverage.

  • Affiliates use acquired LogMeIn access to simulate “remote support” events, which convinces users the infection was an accidental side-effect of a legitimate session.

Stay vigilant—cryptevex’s modular downloader quickly pivots from file encryptor to data wiper if extortion negotiations stall.