A hull scrubber was a form of anti-theft system that was developed for use aboard starships by scientists and technicians in the Hapes Cluster, during the years following the Swarm War. The hull scrubber used controlled bursts of electromagnetic energy to keep a droid or homing beacon from attaching itself to the hull of a starship. One of the drawbacks to using a hull scrubber was that it did not remove pulse-shielded droids, such as combat droids, that could shield themselves from the electromagnetic energy.