Whisper Base was an Imperial military base on the planet Onderon established by Moff Lasre Dardano.
It was built to spy on a political rival of Dardano's; one Admiral Corlen, who was in charge of the garrison in Iziz. To this end it had a powerful signal intelligence array which allowed it to monitor Imperial activity in the system. This, along with the Imperial codes that the base carries, made it a prime target for the Rebel Alliance, who sent a team of infiltrators to capture the listening post.