Design considerations for unattended product in public place
As others have said.. there is no such thing as a people proof box. 

Obviously the "harder" you make the enclosure the more you will slow them down, but you will just p-off somebody enough to get a bigger hammer. 

Keeping it unobtrusive and high off the ground so folks walk by without ever seeing it helps, and a big sticker on the front that says "DANGER! LETHAL VOLTAGES INSIDE!" can also act as a deterrent. 

If you don't want it back after, and plan to replace rather than service, you can always pot the thing up in thermally conductive electrically insulated epoxy, so it's just a big brick.

You can of course also add a siren that goes off if the thing is opened. But you will need someone local to shut it off.

Connectors can be in their own space inside the box only exiting as cables through clamps in U-Shaped cut-outs in the bottom of the box.

Ultimately though there is a cost balance. How much is what is in the box worth versus how much can you afford to pay to stop someone from stealing/destroying it.