This detection rule identifies modifications in the Windows Registry that may indicate an attempt to force the system to revert to NTLMv1 authentication, a process referred to as a "NetNTLMv1 downgrade attack." This change can only be made with local administrator privileges and poses a significant threat as it could facilitate unauthorized access or privilege escalation by enabling weaker authentication protocols. The rule is designed to be used within a specified time frame (now-9m) and monitors several key registry locations where the LmCompatibilityLevel value is modified to potentially insecure settings (0, 1, or 2). The associated investigation steps focus on confirming the legitimacy of the registry change, identifying the responsible user and process, and checking for unauthorized access attempts. False positives can occur with legitimate administrative actions, thus necessitating careful review and exception handling for known benign changes.