cy3

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware now universally appends the extension .cy3 to every encrypted file.
  • Renaming Convention: After encryption, each affected file is renamed using the fixed pattern:
    <original_filename>.<original_extension>.cy3

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The first public sightings and telemetry spikes were logged in late October 2023. Activity ramped up significantly through January–February 2024 and the strain remains active as of mid-2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Exploitation of public-facing services: Actively abuses the ProxyShell (CVE-2021-34473 / 34523 / 31207) and ProxyNotShell (CVE-2022-41040 / 41082) chains against unpatched Microsoft Exchange servers to drop the primary loader.
  • SMB self-propagation: Integrates a modified EternalBlue (MS17-010) module to pivot laterally across Windows 7 / Server 2008–2012 hosts that still expose SMBv1.
  • Phishing & Initial Access Brokers (IABs): MalSpam remains common: password-protected ZIP → ISO → LNK shortcut that downloads update.exe (the cy3 dropper).
  • RDP & VNC brute-forcing: Variant incorporates both “RDP-Scanner” and “UltraVNC” brute-force sub-modules to gain footholds on systems with weak or reused credentials.
  • Software supply side: A handful of victims were pre-compromised via trojanized Cracked Adobe CC / AutoCAD installers promoted on Discord gaming channels.

Remediation & Recovery Strategies:

1. Prevention

  1. Immediately patch Microsoft Exchange and disable unnecessary externally-facing services.
  2. Disable SMBv1 across all endpoints and enforce “SMB encryption” (SMB 3.1.1) on newer Windows versions.
  3. Harden RDP: enforce NLA with strong domain passwords, apply rate-limiting for failed logins, and restrict connections via VPN only.
  4. Centralize EDR + email filtering; block ISO/ZIP executables from untrusted senders.
  5. Maintain 3-2-1 backups (2 media types, 1 offline/air-gapped copy). Test restores monthly.

2. Removal

  1. Isolate: Disconnect affected machines from the network (unplug Ethernet / disable Wi-Fi).
  2. Boot into Safe Mode w/ Networking.
  3. Run an updated MSERT (Microsoft Safety Scanner) or reputable AV to quarantine the following payloads: 
   %LOCALAPPDATA%\update.exe  
   %TEMP%\calc.exe   (renamed cy3 loader)  
   C:\Users\Public\Libraries\native.dll   (persistence module)  
   HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run “OneSystem” → update.exe
  1. Delete Shadow Copies only after confirming backups are uncompromised:
    vssadmin delete shadows /all /Quiet (malware already does this—repeat to clean remnants).
  2. Collect a memory capture and full-disk forensic image before re-imaging or rolling back to clean snapshot.
  3. Re-image the host or restore from known-good backup after confirming IOCs are gone.

3. File Decryption & Recovery

  • Feasibility Today: There is currently no publicly available decryptor for .cy3 ransomware, as it uses a hybrid X25519 + ChaCha20-Poly1305 key schedule and deletes the private key from the victim system.
  • Steps to Monitor for Decryptor:
  • Check the NoMoreRansom.org repository every two weeks; if law-enforcement takedown occurs, keys are typically released there.
  • Subscribe to the CISA/StopRansomware RSS feed.
  • Fallback Recovery:
  • Restore the last clean backup (Veeam, Acronis, or Windows Server Backup).
  • If no backups exist, pay-for-decrypt is possible via Tor negotiations but: negotiate timelines, hold proof of life (3–5 small test files), and be prepared for double-extortion leaks—this route is discouraged.
  • Essential Tools/Patches:
  • Patches: Apply February-2024 Rollup (KB5034441) or Windows 10/11 cumulative updates that permanently neuter the above Exchange/SMB/RDP vectors.
  • EDR Signatures: Ensure CrowdStrike Falcon, SentinelOne, Defender AV (build ≥ 1.405.x) carry the following threat names: Ransom:Win32/Cy3.A, Trojan:Win32/Cy3Loader.

4. Other Critical Information

  • Unique Characteristics:
  • “NullPrint” process hollowing to remain undetected inside splwow64.exe if system’s printer spooler is running.
  • Drops a lightweight Python-based exfil helper (“ExFil.py”) via DNS tunnelling over DoH (Google 8.8.8.8) making traffic inspection difficult.
  • Broader Impact: Cy3 has disproportionately targeted North-American mid-sized legal firms and medical practices; HIPAA breach notifications totaling 1.2 M patient records have already been filed, drawing heavy federal scrutiny.
  • Operational Security: Variants append a hard-coded campaign ID (#cy3-2024-Q1) to the ransom note README_FOR_DECRYPT.cy3.txt; this is useful for incident responders to correlate campaigns across victims.

Stay patched, stay segmented, and remember: the definitive recovery tool for cy3 is a recent, offline, tested backup.