Final answer:
Vibration sensors are required on the walls to detect boundary penetration attempts by sensing mechanical disturbances.
Step-by-step explanation:
In order to detect boundary penetration attempts, the system must have vibration sensors on its walls. Vibration sensors are mechanoreceptors, which are sensory receptors modified to respond to mechanical disturbance. They can detect vibrations caused by someone trying to breach the boundary by bending or touching the walls.