The internal systems probe droid was a model of probe droid designed by Arakyd Industries. Measuring no more than seven centimeters tall, they floated throughout the air ducts of the Galactic Empire's first Death Star battle station, defending against intruders and reporting any unusual findings.
Standard anti-espionage security probes, they were designed to neutralize high-tech infiltrators, usually of the espionage class, using powerful blaster bolts fired from defensive ports, but ignored targets that they lacked specific instructions on how to eliminate. For example, internal systems probe droids did not have programming capable of eliminating rodents. They reported their sensor findings back to the computers to which they answered, where technicians would review the data and see what had triggered the scan.
- "All Creatures Great and Small" (First mentioned)