Cyberdudebivash

 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.

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 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.

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 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.

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 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.

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 Risk Analysis

Factor	Rating	Notes
Sophistication	Medium	Mostly copy-paste, but ChaCha20 + ECIES are strong.
Operational Impact	High	Double extortion → encryption + exfiltration.
Recoverability	Medium	Shadow copies remain if enabled.
Spread Potential	High	Rapid victim expansion across continents.
Detection Difficulty	Medium	Easily detectable due to unpolished execution.

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 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.

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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

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 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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 Contact: iambivash@cyberdudebivash.com

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