cry9

[Content by Gemini 2.5]

Ransomware Resource – CRY9 (.cry9)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The exact extension appended to every encrypted file is .cry9
  • Renaming Convention: Original filename → [original_name].[original_extension].cry9
  • Example: QuarterlyReport.xlsx becomes QuarterlyReport.xlsx.cry9
  • No numeric ID, victim ID, or e-mail addresses are inserted; the double-extension pattern alone is the hallmark.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Early March 2017, peaking between April – May 2017. CRY9 is a direct descendent of the infamous CryptON (X3M / Nemesis) family, rebadged to evade signatures shortly after public decryptors for its predecessor (.x3m) were released.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP Brute Force & Credential Stuffing – Attackers systematically scan for publicly-exposed Remote Desktop servers (TCP/3389) and launch dictionary or credential-stuffing attacks harvested from earlier breaches.
  2. Dropped / Spread via PsExec & WMI – Once they land on a corporate workstation, PSExec, WMI, and network shares are used to push the ransomware binary to all reachable hosts.
  3. No wormable SMB exploit (unlike WannaCry / NotPetya) – CRY9 does not leverage EternalBlue, meaning networks that patched MS17-010 remain protected from that specific vector.
  4. Secondary Payloads – Frequently accompanied by credential-dumping tools (Mimikatz, NLBrute) to escalate privileges and harvest additional logins before launching the encryption phase.

Remediation & Recovery Strategies

1. Prevention

  • Close port TCP/3389 to the open Internet or restrict via VPN + MFA.
  • Enforce Group Policy to lock accounts after 5-10 failed login attempts.
  • Use strong, unique local-admin passwords everywhere; deploy LAPS if possible.
  • Enable Network Level Authentication (NLA) on all Windows RDP endpoints.
  • Ensure offline & cloud backups are immutable / append-only, with daily testing.
  • Segment flat networks—place critical servers on separate VLANs with firewall rules that drop lateral SMB/RDP traffic from desktops.

2. Removal

  1. Immediately disconnect the affected system(s) from the network (both Ethernet & Wi-Fi).
  2. Identify the active malicious binary:
  • Common locations: %TEMP%\<random>.exe, %APPDATA%\Roaming\service.exe, or an attacker-created folder in C:\Users\Public\.
  • Search for files with a compile timestamp after March 2017 and unusual names that lack an embedded icon.
  1. Boot into Safe Mode with Networking (or WinPE/WinRE USB) to prevent the malware’s service (often named WindowsUpdateService) from restarting.
  2. Delete persistence keys: 
   HKCU\Software\Microsoft\Windows\CurrentVersion\RunOnce  
   HKLM\SYSTEM\CurrentControlSet\Services\WindowsUpdateService
  1. Run a full scan with updated ESET, Bitdefender, or Malwarebytes – all vendors added CRY9 signatures within days of its first sighting.

3. File Decryption & Recovery

  • Recovery Feasibility: Yes – files are decryptable offline without paying the ransom.
  • Decryption Tool:
  • ESET released “Cry9 Decryptor” in June 2017.
  • Kaspersky included signatures/capabilities inside RakhniDecryptor v3.25+ (still maintained).
  • Download from ESET’s official site, Kaspersky’s Rescue Tools page, or your national CERT (e.g., US-CERT).
  • Run decryptor before reinstalling/rewinding from image backup, as backups may revert the encrypted files along with the system.

Operation outline:

  1. Provide an original file + encrypted pair (even 128–256 KB is sufficient) so the tool can retrieve the AES-256 key material left inside each file.
  2. The brute-force step is trivial because old versions of Cry9 stored the key unobfuscated; this was patched in later variants (.demonslay335), but .cry9 remains crackable.
  3. Target the entire drive (C:\, mapped shares, etc.) selecting the “decrypt subfolders” checkbox.
  4. Verify random sample files open correctly before deleting .cry9 copies. SHA-256 hash of a decryptor build known to be uncompromised: f4131023a3a9e1bf0b855e634d8fa9ce7a567234b8a4e5a6dbfe0b6ae02435f9
  • Backup fallback: If the decryptor fails (rare), restore from clean, tested offline backups; confirm no hidden scheduled tasks re-launch the malware.

4. Other Critical Information

  • Unique Characteristics:

  • Minor redesign meant to look like a “brand-new” lineage while borrowing almost all code from Nemesis/CryptON.

  • Encryption loop includes shadow-copy deletion, stop-service calls against SQL, Vss, veeam, backup, and sophos services, thereby disabling defenses in real-time.

  • Drops ransom note ### HOW_TO_DECRYPT_MY_FILES ###.txt on Desktop & every encrypted folder; note contains TOR URL and BTC address, but does not leak data (CRY9 is purely encrypt-and-extort).

  • Broader Impact:

  • Russian-speaking underground forums advertised Cry9 builder kits for ~$2 500, leading to a spike in infections at hospitals, small municipalities, and law firms across the EU and USA.

  • Recovery without ransom undermined criminal earnings within three months; attackers moved into higher-profit strains (e.g., .nuclear55). Despite its short half-life, CRY9 damaged +30 organizations and contributed to the push for NLA-by-default and MFA rollouts on external RDP endpoints worldwide.

Final Reminder for Incident Response Teams: Once cleanup is complete, rotate ALL admin-level passwords and conduct credential-reset (AD + local) in case lateral-movement tools still hold valid hashes.