Again, like I said, if someone want in they can do it, but most crooks are smash and crab, and they won't normally walk around with a large tool to do this. Plus this is a very heavy duty lock and case. A vise-grip wouldn't break this heavy duty lock. Plus again, the idea is that it's out of site, and not visible from the car window, since it's under the cargo tonneau cover.
No offense, Ricky, but that setup would slow down a thief by about 3 seconds. Twist that lock with a pair of vise-grips and I'm in your case faster than you can dial 9-1-1. Or a $3 pair of Walmart tin-snips would do a number on the plastic around the lock. Just in case I'm mistaken, and the box is metal. A large tool (like your jack handle) would pop that lock with very little effort. You are suffering from a severe case of 'false sense of security.' If I could get in your garage quietly, I could open that case and be gone before you got your slippers on, if you heard me at all. That said, I hope nobody ever proves this to you.