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Yurei Ransomware — Cyber Threat Analysis Report By CyberDudeBivash | cyberdudebivash.com | cyberbivash.blogspot.com

 


 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

FactorRatingNotes
SophisticationMediumMostly copy-paste, but ChaCha20 + ECIES are strong.
Operational ImpactHighDouble extortion → encryption + exfiltration.
RecoverabilityMediumShadow copies remain if enabled.
Spread PotentialHighRapid victim expansion across continents.
Detection DifficultyMediumEasily detectable due to unpolished execution.

 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.

 CyberDudeBivash Branding & CTA

Author: CyberDudeBivash
Powered by: CyberDudeBivash

cyberdudebivash.com | cyberbivash.blogspot.com
 Contact: iambivash@cyberdudebivash.com

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#CyberDudeBivash #YureiRansomware #ThreatAnalysis #CyberThreatIntel #DoubleExtortion #Malware #BugBounty #ZeroTrust #CyberInsurance

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