I find this question is best phrased with a scenario, so here goes nothing.
Scenario
Tom owns a modem and a router, and gets internet service from Comcast. Tom uses his router to broadcast his own Wi-Fi network.
Tom’s neighbor, George, owns a router. George also uses his router to broadcast a Wi-Fi network, with a different name and password.
Tom offers to split internet costs with George, and George accepts.
Tom runs an ethernet cord from his modem, out of his house, into George’s house, and plugs it into George’s router. Voila, two Wi-Fi networks, one Comcast internet subscription.
George is now up late at night, because he doesn’t quite trust Tom.
Question
Is Tom able to access George’s data from his modem? In other words, is this arrangement a security risk for George?
Underlying more technical question: can one access data from a Wi-Fi network from the modem?
Aside
Originally posted in Network Engineering here, was instructed to re-ask in Super User.
