Designed and developed a custom authentication and access‑control system for IIS using an ISAPI filter, modeled after the capabilities of AuthentiX. The system—called GateKeeper—intercepted HTTP requests at the server layer, enforcing authentication and authorization policies before IIS served any content. It supported both Basic Authentication and Windows Integrated Authentication, giving administrators flexibility in how credentials were handled across different deployment environments. A key driver for the project was a major limitation in IIS at the time: enabling authentication meant creating actual Windows system accounts for every website user. This was impractical and insecure, especially for servers hosting multiple websites. Administrators needed a way to authenticate thousands of site users without granting them the ability to log into the server or appear as OS‑level principals. GateKeeper solved this by introducing a fully independent user store and permission model, decoupled from Windows accounts while still integrating cleanly with IIS request handling. GateKeeper also included a Windows‑based administration console built in Delphi, providing a user‑friendly interface for managing users, groups, and permissions. While inspired by AuthentiX’s goal of simplifying access control for large user bases, GateKeeper was purpose‑built for internal enterprise use, with custom logic, extensibility points, and deployment‑specific behaviors that aligned with the organization’s infrastructure and security requirements.