The disclosed technique involves achieving persistence on Windows systems by manipulating the NTUSER.MAN file located in the %USERPROFILE% directory rather than performing direct registry writes to HKCU that trigger registry callbacks. Traditional EDR solutions often monitor registry callback APIs to detect suspicious persistence mechanisms. However, this method circumvents such detection by only writing to the NTUSER.MAN file, which is a registry hive file representing the user's registry settings, without invoking registry callback functions. This stealth approach allows attackers to maintain medium integrity persistence, meaning they can survive reboots and maintain footholds without requiring elevated privileges or triggering common detection heuristics. The technique was revealed on Reddit NetSec and has been held confidential for approximately 18 months, indicating its novelty and potential effectiveness. While no active exploitation has been reported, the method’s ability to evade detection makes it a significant concern for defenders relying on conventional EDR registry monitoring. The lack of direct registry API calls means that defenders must look beyond standard callback monitoring and consider file system monitoring of NTUSER.MAN and behavioral analytics to detect anomalous persistence attempts.

For European organizations, this technique could enable attackers to establish persistent access on Windows endpoints without detection by common EDR solutions, increasing the risk of prolonged intrusions and data exfiltration. Medium integrity persistence allows attackers to maintain footholds with user-level privileges, which can be escalated or leveraged for lateral movement. The stealth nature of the technique complicates incident response and forensic investigations, potentially delaying detection and remediation. Organizations with high reliance on Windows desktops and laptops, especially those in critical infrastructure, finance, and government sectors, face increased risk. The technique’s evasion of registry callback monitoring could render existing EDR solutions less effective, necessitating upgrades or additional detection layers. This may lead to increased operational costs and risk exposure if not addressed promptly.

To mitigate this threat, European organizations should implement enhanced monitoring of the NTUSER.MAN file for unauthorized or suspicious modifications, as this file is the persistence vector. Endpoint security solutions should be configured or updated to include file integrity monitoring specifically targeting user registry hive files. Behavioral analytics and anomaly detection systems should be employed to identify unusual user profile or registry hive activity that does not correspond with legitimate user actions. Organizations should also conduct regular audits of persistence mechanisms and employ threat hunting focused on non-standard persistence techniques. Deploying advanced EDR solutions capable of detecting file-based persistence and integrating telemetry from multiple sources can improve detection capabilities. User education on phishing and social engineering remains critical to prevent initial compromise that could lead to persistence establishment. Finally, maintaining up-to-date backups and incident response plans will reduce the impact of potential intrusions leveraging this technique.