yurei is a ransomware operator no longer publishing new disclosures. Darkfield has indexed 3 public victims claimed by this operator between September 5, 2025 and September 9, 2025. Yurei is an emerging ransomware group first observed in September 2025, operating with apparent financial motivations based on their targeting patterns and victim selection. The group's origin and potential affiliations remain unclear due to limited public documentation, though their diverse geographical targeting across Switzerland, Sri Lanka, and Nigeria suggests either opportunistic attacks or access to varied initial compromise vectors. Given the recent emergence and limited intelligence available, their attack methodology, specific tools, and encryption techniques have not been extensively documented by major security firms or government agencies. The group appears to focus on energy sector targets where data is available, though their small victim count of three documented cases suggests they are either highly selective, newly operational, or operating below the radar of major threat intelligence providers. Yurei remains active as of their recent emergence, though the limited public intelligence makes it difficult to assess their operational tempo, sophistication level, or long-term persistence in the ransomware landscape.
How we know this. Operator profiles on Darkfield are built from continuous monitoring of every leak site the group is known to operate, cross-correlated with community-curated feeds (RansomLook, ransomware.live, RansomWatch, MISP-galaxy). Status flips from active to inactive when no new disclosure appears for 60 days. MITRE ATT&CK mappings shown in the interactive section below are sourced from CISA, vendor analysis, and the MITRE community catalog — we attribute each technique back to its source. Aliases reflect operator re-brands and affiliate splits.