Ransomware Research
Fenrir Ransomware
Fenrir is a malicious ransomware strain that encrypts victim files and demands ransom payment for decryption. First observed in the wild on July 1, 2017, this ransomware has been actively targeting systems worldwide.
Quick Facts
- Ransomware Family
- Fenrir
- First Seen
- July 1, 2017
How Fenrir Ransomware Works
Targeted Files
Requires C&C to send and receive information
File Encryption Patterns
Fenrir modifies encrypted files using specific patterns to mark them as encrypted:
File extensions added after encryption:
./\.[0-9A-F]{10}$/Ransom Note and Payment Demands
After encrypting files, Fenrir displays ransom notes demanding payment for file recovery:
ransom.rtfRansom message:
notes/ransom.rtf
Note locations:
TempRansom message:
notes/note.txt
Note locations:
OnceOnCompletionTechnical Indicators
Associated Executable Files
The following executable files are associated with Fenrir ransomware:
Adobe Reader.exe
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About This Analysis
This Fenrir ransomware analysis is part of Elastio's comprehensive ransomware detection database. Elastio provides advanced ransomware protection and recovery solutions, helping organizations defend against and recover from ransomware attacks like Fenrir.
Last updated: July 30, 2025