Tamper detecting enclosures are described. In one configuration, an inflated balloon at least partially surrounds a module in an enclosure and biases at least one normally opened switch into a closed position during normal operation. If an attacker attempts to attack the enclosure, the balloon should at least partially deflate and cause the switch to return to its normally opened position thereby detecting the attack. In another configuration, the balloon is adhered to the inside wall of the outer enclosure.