It's certainly unauthorized access if you intentionally built it with the goal of harming other peoples systems, especially if you hid that action from them the way our self-righteous friend here did.

You are authorized to do what the user agreed to, no more. Further the agreement must be reasonable. Exploiting the victims system to intentionally cause harm isn't reasonable.

F-secure once included a clause to use their wifi that you "assign their first born child to us for the duration of eternity." It was funny, but not legally enforceable and would have offered them no legal shelter if they'd gone out on a kidnapping spree that night.