This detection rule identifies potential misuse of ngrok in conjunction with Remote Desktop Protocol (RDP) services on Windows systems. Ngrok is a tunneling service that can expose local servers behind NATs or firewalls to the public internet, thus allowing an external party to access services that are otherwise protected. The rule specifically looks for Event ID 21 that indicates remote desktop services being established or modified, with an address that appears to be derived from the local host address (often represented in network logs as '16777216'). The use of ngrok in this context can signify that an attacker is attempting to bypass traditional security measures, provide external access to RDP services, or control compromised systems. Notably, such activity could enable unauthorized access, data exfiltration, or lateral movement across networks, making it important to monitor and investigate any findings related to this rule. Detection of such activity should invoke a high level of response due to its association with command and control (C2) tactics within the MITRE ATT&CK framework.