I have two local computers both connected to the internet with Linksys router (ethernet). One is used by me and the other by another user. I want to be able to enable and disable Internet access on the other computer, from my computer (not physically) and if it is disabled the user will not be able to enable it. And the other user would need a password to enable it again. How would I do this, Im sure it would have to be a separate program. NOTE: I'm not asking for RealVNC, LogMeIn, GoToMyPC, etc. I need something that works in the background without the user noticing.
Block outward traffic from an IP address(the other user's PC) in the router admin interface. Most routers support this sort of traffic routing/managing.
Yeah, most routers have a web interface that you can access from any networked computer through your browser. Check your manual.