RegretLocker is a ransomware family discovered in late 2020 that targets Windows operating systems without specific version constraints. The malware incorporates unique evasion techniques, notably performing checks against a particular username and PC name ("WIN-295748OMAKG"); if either matches, the malware terminates immediately, likely to avoid execution in controlled or analysis environments. Persistence is achieved by creating a Windows Scheduled Task named "Mouse Application" that runs every minute using the Schtasks.exe utility invoked through cmd.exe and ShellExecuteA, ensuring continuous execution and complicating removal efforts. The malware is distributed via a publicly accessible URL (http://344744.cloud4box.ru/files/locker/locker.exe) and communicates with an IP address (109.248.203.209), which may serve as command and control infrastructure or for data exfiltration. Although there are no known exploits actively used in the wild or widespread campaigns, the malware demonstrates moderate sophistication with a threat level and analysis rating of 2. No patches or affected Windows versions are specified, suggesting broad targeting. Technical analyses and reverse engineering reports provide insights into its behavior, but public data on its prevalence and impact remain limited. Overall, RegretLocker represents a ransomware threat with evasion and persistence capabilities that could disrupt operations and compromise data confidentiality if deployed effectively.

For European organizations, RegretLocker presents a moderate risk primarily through its ransomware functionality, which can encrypt critical data, causing operational disruption and potential financial losses from ransom payments or recovery efforts. Its persistence mechanism via scheduled tasks allows it to maintain a foothold on infected systems, increasing potential downtime and complicating incident response and remediation. The evasion technique of checking for specific usernames and PC names may hinder detection by security tools, delaying response and increasing damage potential. Although no active exploitation campaigns are currently documented, the availability of a public payload and associated command and control infrastructure indicates potential for targeted or opportunistic attacks. Organizations handling sensitive or critical data could face confidentiality breaches if data exfiltration occurs prior to encryption. Operational impacts include loss of data availability, reputational damage, and increased complexity in incident handling. Given the medium severity and limited exploitation evidence, the immediate threat level is moderate but could escalate if threat actors adopt or evolve this malware to target European entities more aggressively.

European organizations should implement specific measures beyond generic ransomware defenses to mitigate RegretLocker risks: 1) Monitor and restrict the creation and execution of scheduled tasks, especially those named "Mouse Application" or tasks invoking Schtasks.exe at frequent intervals, to disrupt the malware's persistence mechanism. 2) Deploy behavioral detection capabilities to identify malware performing environment checks for specific usernames or PC names, enabling early detection of evasion attempts. 3) Block network access to known malicious URLs and IP addresses associated with RegretLocker, such as http://344744.cloud4box.ru/files/locker/locker.exe and IP 109.248.203.209, using firewalls, web proxies, and DNS filtering. 4) Conduct proactive threat hunting focused on identifying unusual scheduled tasks and persistence artifacts indicative of RegretLocker infection. 5) Harden endpoint security by enforcing application whitelisting and restricting execution privileges to prevent unauthorized binaries from running. 6) Maintain offline, regularly tested backups to ensure rapid recovery without paying ransom. 7) Educate users on phishing risks and suspicious downloads, as initial infection vectors are likely social engineering-based. 8) Engage with threat intelligence sharing platforms to stay updated on RegretLocker developments and emerging indicators of compromise.