RegretLocker is a ransomware malware family identified and analyzed in a VMRay Analyzer report for a specific sample (#1500977). The malware exhibits multiple sophisticated behaviors typical of ransomware threats, including establishing outbound TCP and HTTP connections, DNS requests, and external IP checks to communicate with command and control (C2) servers. It uses encryption APIs to encrypt victim data, modifies Windows backup settings to hinder recovery, and installs persistence mechanisms such as startup scripts via registry modifications and scheduled tasks using schtasks. The malware also employs evasion techniques like delaying execution through sleep functions and scheduled task delays, creating named mutexes to prevent multiple instances, and hiding process windows. It drops PE files and dynamically uses Windows APIs, enumerates running processes, and changes folder appearances to potentially mislead users or security tools. The malware has been flagged with low severity but demonstrates multiple attack patterns consistent with ransomware operations. There are no known exploits in the wild linked to this sample, and no specific affected software versions are listed. The threat level is moderate (3 out of an unspecified scale), with an analysis confidence of 2, indicating some uncertainty. The malware’s tactics suggest it targets Windows environments and aims to encrypt data while disabling recovery options, typical of ransomware aiming for financial extortion.

For European organizations, RegretLocker poses a risk primarily to Windows-based systems, especially those with inadequate endpoint protection or lacking robust backup strategies. The encryption of data and modification of backup settings can lead to significant operational disruption, data loss, and financial costs related to ransom payments or recovery efforts. The malware’s ability to establish external connections could facilitate data exfiltration or further compromise. Although currently assessed as low severity, the presence of multiple persistence and evasion techniques means infections could persist undetected, increasing potential damage. Critical infrastructure, healthcare, finance, and manufacturing sectors in Europe could face operational downtime and reputational damage if targeted. The lack of known widespread exploitation suggests a limited current impact but does not preclude future campaigns leveraging this malware. The threat is particularly concerning for organizations with insufficient network segmentation or outdated security controls.

European organizations should implement layered defenses beyond generic advice. Specifically, they should: 1) Enforce strict application whitelisting to prevent unauthorized execution of dropped PE files. 2) Harden Windows environments by restricting registry modifications and scheduled task creations to privileged users only. 3) Monitor and alert on unusual network activity, such as unexpected outbound TCP or HTTP connections and DNS queries to suspicious domains. 4) Regularly audit and protect Windows backup settings to prevent unauthorized changes. 5) Deploy endpoint detection and response (EDR) solutions capable of detecting behaviors like process enumeration, API hooking, and mutex creation. 6) Implement robust, immutable, and offline backups to ensure recovery without paying ransom. 7) Conduct user awareness training focused on ransomware infection vectors. 8) Use threat intelligence feeds to update detection rules for RegretLocker indicators. 9) Employ network segmentation to limit lateral movement if infection occurs. 10) Regularly patch and update all systems to reduce attack surface, even though no specific vulnerable versions are noted for this malware.