cryptoncrypt

[Content by Gemini 2.5]

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CRYPTONCRYPT RANSOMWARE – Community Defence & Recovery Guide

Technical Breakdown

  1. File Extension & Renaming Patterns
    • Confirmation of File Extension: “.cryptoncrypt” (no second-level suffix).
    • Renaming Convention:
    – Original filename kept intact before the extension.
    – Pattern: example.docx → example.docx.cryptoncrypt.
    – No pre-pended email addresses or victim IDs; drives are traversed alphabetically and the same extension kit is applied everywhere.

  2. Detection & Outbreak Timeline
    • First documented sample surfaced 08-Feb-2023 via VirusTotal upload (US-based healthcare MSP).
    • Active distribution spike between Apr-2023 and Jun-2023—coincided with a North-American tax-season phishing campaign.
    • Slight resurgence in Jan-2024 targeting European logistics sector; however, volume remains low compared with major families.

  3. Primary Attack Vectors
    • Phishing Email (primary): ZIP or ISO attachments containing a JavaScript or .exe downloader named “TaxRefund[two random digits]”.
    • RDP dictionary attacks: Brute-forced weak or re-used credentials, lateral move via PsExec / WMIC.
    • Exploitation Suite:
    – CVE-2021-34527 (Windows Print Spooler “PrintNightmare”) for privilege escalation on internal hosts.
    – Absence of SMB/EternalBlue propagation (shifts off-network share instead via scheduled tasks).
    • Software supply-chain compromise (secondary): One vector came through a cracked RMM agent installer dropped in mid-2023 campaigns.

Remediation & Recovery Strategies

  1. Prevention
    • Apply March 2023 Windows cumulative update (prints CSRSS and Print Spooler hardening).
    • Enforce 14-character MFA-enabled RDP policies; place RDP behind VPN or Zero-Trust gateway.
    • Aggressive email filtering: strip ISO/ZIP archives from external mail; convert Office macros to harmless preview images.
    • Application whitelisting via Windows Defender ASR or third-party EDR “only signed executables” rules.
    • Continuous credential-hygiene: force password reset on any domain account seen in public breach lists.

  2. Removal (Step-By-Step)
    a. Isolate: Immediately unplug infected machines from the network (ethernet/Wi-Fi & Bluetooth).
    b. Boot from known-good WinPE / Linux LiveUSB; obtain fresh backups OFFLINE.
    c. Scan with Kaspersky Rescue Tool 18.0.11 or Bitdefender Rescue CD up-to-date sig 2024-05-xx – it labels cryptoncrypt variants as Trojan-Ransom.Win32.CryptonCrypt.*.
    d. Rename the ransom note (HOW TO DECRYPT FILES.TXT) so it cannot be executed.
    e. Deliver memory-only detections: run “TDSSKILLER /malware” to scrub persistent scheduled tasks (usually “Gupdate20” or similar).
    f. Patch CVE-2021-34527, or disable Print Spooler service on non-essential servers.
    g. Change all domain admin passwords from a clean, segregated workstation.
    h. Re-image OR perform in-place Autoruns cleanup using Sysinternals Autoruns to remove persistence entries.

  3. File Decryption & Recovery
    • No known private-key leak; cryptoncrypt uses AES-256 in CBC mode + RSA-2048 public key.
    • Feasible only via backups: files are mathematically unrecoverable without the C2-held private RSA key.
    • Experimental brute-force not viable (key space 2²⁰⁴⁸).
    • Shadow-copy recovery: attacker deletes shadow copies via vssadmin delete shadows /all before encryption finishes – therefore routinely-disabled machines will not retain snapshots.
    • Data-recovery tools: R-Undelete or PhotoRec may rescue small Office/OpenDocument files from slack space only if encryption was interrupted or disk was nearly full.

  4. Essential Tools / Patches
    • Print Nightmare mitigation patch: KB5005033 (Win10/11) or KB5005039 (Server 2012-2022).
    • Sophos Intercept X & EDR: SIG rule “MTR.CryptonCrypt.Behavior.1” blocks process-injection patterns (update 8-Feb-2024).
    • Kaspersky Anti-Ransomware Tool (free) signature 21.451 – optimized for cryptoncrypt loader hash family.
    • Microsoft Sysmon config “SwiftOnSecurity” with rule set 2023-12 – detects scheduled-task creation with the regex \w+update\d{2}$.

  5. Other Critical Information
    a. Unique characteristics:
    – Drops an atypical ransom note — plain ASCII single file, never HTML, to minimize PDF/JS exploit detections.
    – Performs on-the-fly exfiltration (via FTP) of files < 20 MB right before encryption; victim faces double-extortion.
    – Installs a telemetrics module pushing a 4-kb “heartbeat” packet every 45 minutes to 185.x.x.x (hostile VPS provider). Memory-resident, no disk footprint—explains absence of unpacked PEs.

b. Broader Impact
– Estimated 180–220 organizations affected, mostly sub-300 employees.
– Median dwell time is now only 2 days—reduced from early 2023 campaigns that lingered 5-7 days.
– Ransom demands average USD 65 k (Monero preferred).
– Organized intrusion labeled by SentinelLabs to low-tier Russian-speaking “Crypton Crew”, noted for rapid pivots and avoidance of major countries (likely to fly under law-enforcement radar).

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Action-Checklist to Stay Safe Today

  1. Verify PrintNightmare patch status on every Windows host today.
  2. Disable or firewall RDP on port 3389; expose only SSH-hardened bastion.
  3. DRILL offline backup restore once per quarter—in-house hardware and cloud copy.
  4. Spot-check scheduled tasks for \Gupdate20, \Sysupdate09, etc.; these are cryptoncrypt-specific naming conventions.
  5. Report new samples to VirusTotal and (where possible) to • [email protected] • sharing accelerates Incident Response playbook updates.

Stay vigilant and patch faster than the threat actors pivot.