Introduction

The rise of open-source ransomware projects has lowered the barrier for cybercriminals to launch sophisticated attacks with minimal coding effort. In September 2025, a new player entered the field — Yurei Ransomware.

Built upon the leaked Prince-Ransomware source code, Yurei shows how script-kiddie-level threat actors can quickly adapt existing code and launch impactful ransomware campaigns with double extortion models.

This CyberDudeBivash report provides a deep-dive analysis of Yurei’s techniques, tactics, weaknesses, indicators of compromise (IoCs), and mitigation strategies for enterprises and security researchers.

 Technical Breakdown

 Code Base & Language

• Yurei is written in Go (Golang).

• Derived almost entirely from Prince-Ransomware.

• Contains debug symbols and module names — a major oversight by the attackers.

 Encryption Mechanism

• ChaCha20 for per-file symmetric encryption.

• Each file gets a random key + nonce.

• Keys protected with ECIES (Elliptic Curve Integrated Encryption Scheme).

• Encrypted files are renamed with .Yurei extension.

 Speed & Concurrency

• Uses Go goroutines to encrypt drives in parallel.

• Monitors newly connected network shares and encrypts them on the fly.

 Ransom Note & Negotiation

• Drops ransom note: _README_Yurei.txt.

• Victims are directed to a Tor (.onion) portal for payment negotiation.

• Attempts to set wallpaper via PowerShell — but the URL is missing, so it fails.

 Weaknesses

• Fails to delete Shadow Copies → enabling potential recovery.

• Left symbols in binary → easier reverse engineering.

• Poor operational security — suggests amateur operators.

 Impact & Victimology

• First victim: Sri Lankan food manufacturing firm.

• Spread to India and Nigeria in less than a week.

• Target sectors: manufacturing, mid-sized enterprises, poorly defended orgs.

• Suspected origin in Morocco, based on infrastructure analysis.

 Indicators of Compromise (IoCs)

• Encrypted file extension: .Yurei

• Ransom note: _README_Yurei.txt

• Binary with Go debug symbols intact.

• PowerShell command attempts wallpaper change via:

  rundll32.exe user32.dll, SystemParametersInfo
  

• Outbound traffic to Tor-based negotiation sites.

 Risk Analysis

 CyberDudeBivash Defensive Recommendations

1. Backup Strategy

   • Maintain immutable & offline backups.

   • Ensure Volume Shadow Copy Service (VSS) is enabled.

2. EDR/AV Signatures

   • Look for .Yurei extensions, _README_Yurei.txt.

   • Detect parallel file access spikes in Go binaries.

3. Network Segmentation

   • Restrict network share access.

   • Monitor for unusual SMB drive enumeration.

4. Threat Intel Integration

   • Add Yurei IoCs to SIEM & SOAR workflows.

   • Watch for connections to newly registered Tor onion services.

5. Incident Response

   • Include data exfiltration scenarios in playbooks.

   • Prepare legal, regulatory, and PR response to extortion.

Highlighted Keywords

This analysis covers:

• Ransomware incident response services

• Cyber insurance for ransomware attacks

• Managed detection & response (MDR)

• Zero Trust ransomware defense models

• Cloud ransomware recovery solutions

• Endpoint security & EDR platforms

• Data breach litigation and compliance services

 Conclusion

Yurei demonstrates how open-source ransomware projects amplify global threats.

• Strengths: ChaCha20 encryption, concurrency, double extortion.

• Weaknesses: Debug symbols, poor OPSEC, Shadow Copy failure.

For defenders, Yurei is a reminder that even amateur attackers can build powerful ransomware when open-source code is abused.

 CyberDudeBivash recommends behavioral detection + strong backup strategies as the most effective countermeasures against Yurei and future ransomware families.

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