The setup is an AT&T broadband connection with a modem-router that provides both phone and internet. Also, I presume, a LAN since there are four ethernet outputs from the device and WiFi is also available.
I know I can crawl around back and pull the ethernet cable but that isn't very convenient and might lead to malfunction of the cable plug or the ethernet port from over use. I want to be able to not be connected most of the time but (hopefully) have something as easy as closing a switch when I need to get online.
Needing to provide a password, as though using a dial-up modem, any time I want to connect is quite acceptable as long as my computer is truly not accessible to the network once I sign off. If this can be done purely with software, that might be ok if very reliable (very hard to hack).