Gunra ransomware is a newly identified ransomware threat that surfaced in April 2025, notable for its Dedicated Leak Site (DLS) used to pressure victims into paying ransom. The ransomware's codebase shows significant similarities to the infamous Conti ransomware, indicating that Gunra likely leverages the leaked source code of Conti. This connection suggests a sophisticated lineage and potentially similar attack methodologies. Gunra employs a hybrid encryption scheme combining RSA asymmetric encryption with the ChaCha20 symmetric cipher, a modern and efficient algorithm, to encrypt victim files. It selectively excludes certain folders and file types from encryption, which may be a tactic to maintain system stability or avoid detection. The ransomware drops a ransom note named 'R3ADM3.txt' to inform victims of the attack and payment instructions. A notable aggressive tactic Gunra uses is a time-based pressure mechanism that forces victims to initiate ransom negotiations within five days, increasing psychological pressure and urgency. Additionally, Gunra deletes volume shadow copies on infected systems, a common ransomware technique to prevent victims from restoring files via Windows' native backup mechanisms, thereby increasing the likelihood of ransom payment. The ransomware is associated with multiple MITRE ATT&CK techniques including T1489 (Service Stop), T1106 (Execution through API), T1083 (File and Directory Discovery), T1566 (Phishing), T1078 (Valid Accounts), T1486 (Data Encrypted for Impact), T1059.003 (Command and Scripting Interpreter: Windows Command Shell), and T1490 (Inhibit System Recovery). Indicators of compromise include multiple file hashes provided by AlienVault OTX. While no known exploits in the wild have been reported yet, the presence of a DLS and aggressive negotiation tactics indicate an active and evolving threat. Organizations are advised to maintain robust security postures, including patch management, regular backups, and user awareness training to mitigate phishing and credential compromise risks.

For European organizations, Gunra ransomware represents a significant operational and financial risk. The encryption of critical files combined with deletion of volume shadow copies severely impairs recovery efforts, potentially leading to prolonged downtime and data loss. The use of a DLS increases reputational damage risks, as stolen data may be publicly leaked if ransoms are not paid, which could also lead to regulatory penalties under GDPR for data breaches. The five-day negotiation pressure tactic may force hasty decisions, increasing the likelihood of ransom payment and financial loss. Sectors with high-value data such as healthcare, finance, manufacturing, and critical infrastructure are particularly vulnerable. The ransomware’s similarity to Conti suggests it may adopt similar lateral movement and privilege escalation tactics, increasing the risk of widespread network compromise. European organizations with insufficient segmentation, weak credential management, or poor user training are at elevated risk. The threat also complicates incident response due to its sophisticated encryption and anti-recovery measures, potentially increasing incident response costs and operational disruption.

1. Implement robust network segmentation to limit lateral movement within corporate networks. 2. Enforce strict multi-factor authentication (MFA) on all remote access and privileged accounts to reduce the risk of credential compromise. 3. Conduct regular phishing awareness training tailored to recognize social engineering tactics associated with ransomware delivery. 4. Maintain frequent, tested offline and immutable backups to enable recovery without paying ransom; ensure backups are isolated from the main network. 5. Monitor for indicators of compromise such as the provided file hashes and unusual file encryption activity. 6. Deploy endpoint detection and response (EDR) solutions capable of detecting ransomware behaviors, including volume shadow copy deletion and suspicious encryption processes. 7. Apply the principle of least privilege to limit user and service account permissions. 8. Regularly update and patch all systems and software to close vulnerabilities that could be exploited for initial access. 9. Establish and rehearse incident response plans specifically addressing ransomware scenarios, including communication strategies for DLS exposure. 10. Monitor threat intelligence feeds for updates on Gunra TTPs and indicators to adapt defenses promptly.