I work at a computer store where there is a computer that is meant to be used by the customers to do research on products. However, some customers use this computer to check their emails from the likes of yahoo and Hotmail, preventing other customers from using it for intended purposes. I know that I can go into the router and block these web-based email services via URL blocking. However, the employees at the store do use this computer for their own emails which I think is ok. The problem is how can I tell the router to selectively exempt certain users from this URL blocking? I am sure this involves some kind of authentication to the router. But I am not sure how this is done. (I have full access to the configuration of the router).