Are entry door systems with lock release secure?
If I am inferring correctly what you are describing, it sounds like the "brains" of the system are installed outside with one screw access. That, of course, is an abysmal design. The only thing that should be outside accessible would be the wires to the call button and speaker - all other wiring should be inside-access only.

If you are otherwise happy with the system, you could probably move the components that should not be outside inside, leaving only the wiring needed for the outside components running to the outside box.