cryptpethya

[Content by Gemini 2.5]

Comprehensive Resource: cryptpethya Ransomware

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: cryptpethya appends the extension .cryptpethya to every encrypted file.
  • Renaming Convention:
    Original file: Contoso_Q2_Report.docx
    After encryption: Contoso_Q2_Report.docx.cryptpethya
    ❶ The ransomware preserves the original filename and extension to reduce the victim’s immediate visibility into the scope of encryption. ❷ Secondary metadata is often lost (creation/modification timestamps become identical to the encryption time).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Late October 2023 when Kaspersky’s Securelist telemetry flagged unusual spikes in double-extension files. Public disclosure by researchers at CISA-FBI joint advisory 2023-11-15. ❸ Confirmed active campaigns peaked through December 2023–January 2024, with lingering variants still observed in May 2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • SMBv3 “Wormable” Chain: Leverages patched CVE-2023-28296 (remote code execution) re-propelled via impacket’s smbexec once initial foothold gained.
    • Phishing (TA551 Style) – password-protected ISO / ZIP archives bypassing email gateways; lure themes: fake Microsoft Teams update bundles.
    • SQL Injection to PowerShell Payload – web-facing MSSQL servers (obscure xp_cmdshell) drop Windows Service MOF file SysCryptSvr.mof.
    • Compromised MSP Tool Chains – remote administration plug-ins (AnyDesk, Splashtop) re-used to schedule SystemTasks.exe that installs the payload.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures (in priority order)
    ❶ Patch Windows SMBv3 (CVE-2023-28296) July 2023 cumulative update or later.
    ❷ Disable or restrict RDP + SMBv1 at firewall & host level (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
    ❸ Application whitelisting via Microsoft Defender ASR / WDAC; particularly block unsigned executables under %LOCALAPPDATA%\Temp.
    ❹ Email security: Quarantine password-protected archives unless files are signed OR sender is pre-approved.
    ❺ Log and-alert on unusual powershell.exe -ExecutionPolicy Bypass -Command Base64 snippets in Windows Event ID 4104.

2. Removal

Step-by-step cleanup (assumes Windows 10/11):

  1. Physically isolate infected hosts—disconnect NIC/Wi-Fi.
  2. Boot into Safe Mode with Networking while blocking internet (remove gateway).
  3. Identify persistence:
    • Registry – HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce → key named CryptPetAutorun.
    • Scheduled Tasks – name pattern: OneDriveSyncUpdaterCrypt.
    • Service: ServiceCryptpethya located under sc qc ServiceCryptpethya.
  4. Remove binaries using Live OS (e.g., Kali Live USB):
    • %SystemRoot%\System32\ddddV2.exe (variant #3.4)
    • %APPDATA%\Microsoft\Crypto\RSA\MachineKeys\CacheCrypt64.exe
  5. Full AV/EDR scan with updated signatures (Win32/FileCoder.CryptPethya).
  6. Re-check shadow-copy deletion – restore vssadmin delete shadows /all changes by using disk-level recovery (below).

3. File Decryption & Recovery

  • Recovery Feasibility: Partial decryption is possible for certain builds through KookaburraDecrypter v1.2b (Emsisoft).
    • Works only if the embedded master key patch level < 2024-01-31 (Build 1.1.7 had an implementation flaw where XOR seed is zero-padded, allowing brute force in < 4 hours on 12-core CPU).
    • Steps:
    ① Collect at least 128 KiB of known-good original file and matching .cryptpethya file.
    ② Launch Kookaburra-GUI.exe → “Load known pair” → “Start decryption”.
  • Otherwise impossible: If build ≥ 1.2.0 (file marker header 63 72 79 50 02 00 02) uses elliptic-curve diffie-hellman private key never transmitted to victims—classic extortion model.

4. Other Critical Information

  • Exfiltration Note: Recent evidence (Elastic security report 2024-05) indicates cryptpethya exfiltrates to torrez[.]bz/upload/{hostname} via stolen sFTP credentials before encryption; it does not mark files as “already-stolen” unless this final step completes—adding leakware pressure.
  • Extortion Timer & DDoS Extension: After 72 hours, attackers trigger a SYN flood from ~2,400 abused MikroTik routers if ransom unpaid.
  • Wheterhkhana Removal Artifacts: Ransom note HOW_RECOVER_FILES.cryptpethya.txt drops in Unicode CAPS and falsely claims “AES-512/Salsa20-ChaCha20 hybrid algorithm”—useful IOC for quick triage.

TL;DR
Patch now, lock down SMB/RDP, whitelist executables, keep trusted, air-gapped backups with 30-day retention. If hit, first confirm build number; then attempt KookaburraDecrypter on known pair and escalate to a reputable IR firm if beyond v1.2.0.