Cybersecurity firm Profero has successfully reverse-engineered the encryption mechanism used by the DarkBit ransomware group, enabling victims to recover their files without paying a ransom. This development disrupts the ransomware-as-a-service (RaaS) economy and provides a rare win for defenders against one of the most aggressive encryption-based threats in 20251. The breakthrough centers on DarkBit’s implementation of AES-256, which Profero exploited to create a free decryption tool now available through the No More Ransom project2.
TL;DR: Key Points
- Profero cracked DarkBit’s AES-256 encryption, appending
.Darkbitextensions to files - Decryption tool released via No More Ransom project, bypassing ransom demands
- DarkBit operators threatened data leaks within 48 hours of infection3
- Attack chain resembles Bank Sepah incident with wiper-class tooling4
Technical Analysis of the Encryption Flaw
DarkBit’s encryptor used a deterministic key generation process that allowed Profero to reconstruct decryption keys without the attacker’s master key. Forensic analysis revealed the ransomware generated keys using system metadata (volume serial numbers, file timestamps) combined with a hardcoded salt value5. This deviation from cryptographically secure random number generation created a recoverable pattern.
The ransomware appended the .Darkbit extension and dropped a ransom note titled READ_ME.txt, threatening to publish exfiltrated data on dark web leak sites if payment wasn’t made within 48 hours. Profero’s tool works by:
- Scanning for encrypted files with the
.Darkbitextension - Rebuilding the encryption key using harvested system parameters
- Processing files through a modified OpenSSL library for batch decryption
Operational Impact and Case Parallels
The Bank Sepah attack in June 2025 demonstrated DarkBit’s destructive capabilities when payment demands went unmet. Attackers deployed wiper modules that:
| Impact Area | Duration |
|---|---|
| Core banking systems | 50+ days downtime |
| ATM networks | Manual processing required |
| Historical records | Pre-29 June data erased |
Profero’s decryption tool cannot recover files from wiper-enabled attacks, emphasizing the need for immutable backups. The 3-2-1 backup rule (3 copies, 2 media types, 1 offsite) proved critical for organizations that restored operations without paying ransoms6.
Mitigation Strategies
For systems still vulnerable to DarkBit infections:
“Isolate infected systems immediately and run Profero’s decryption tool from clean media. Shadow copies may survive if Volume Shadow Copy Service (VSS) wasn’t disabled during the attack.”
— Mike Cobb, DriveSavers Director of Engineering7
Enterprise defenders should prioritize:
- Network segmentation to limit lateral movement
- Regular testing of backup restoration procedures
- Phishing simulations targeting finance teams (60% reduction in infections8)
Conclusion
Profero’s decryption breakthrough demonstrates that even sophisticated ransomware can contain cryptographic flaws. While the tool provides relief for current victims, DarkBit’s operators will likely adapt their encryption methods. Organizations must combine technical controls like immutable backups with human-focused defenses to mitigate evolving ransomware threats.
References
- DriveSavers. (2025). Ransomware Data Recovery.
- No More Ransom Project. (2025). Decryption Tools Repository.
- PCRisk. (2025). DarkBit Ransomware Technical Analysis.
- Reuters. (2025). Bank Sepah Cyberattack Analysis.
- CrowdStrike. (2025). Ransomware Recovery Guide.
- NAKIVO. (2023). 3-2-1 Backup Rule Implementation.
- DriveSavers. (2025). Ransomware Recovery Case Studies.
- CrowdStrike. (2025). Phishing Simulation Efficacy Data.
