A Vulcan listening post (2151).
A Klingon listening post (2293).
A listening post is a covert operations center for monitoring communications and territory (as of an enemy) between space-faring civilizations.
In 2151, Captain Archer uncovered a Vulcan listening post hidden at the temple of P'Jem affirming Andorian suspicions. (ENT: "The Andorian Incident")
In 2293, the Enterprise-A fooled its way past a Klingon listening post on Morska to rescue Captain Kirk and Doctor McCoy from Rura Penthe. (Star Trek VI: The Undiscovered Country)
In 2373, a Federation listening post in the Gamma Quadrant intercepted a Cardassian message, discovered to be an encoded message from Enabran Tain, though Garak initially claimed it was a five-year old planetary survey report. (DS9: "In Purgatory's Shadow") During the Dominion invasion that followed, Kira Nerys noted that the last Federation listening post just went dead shortly before the fleet entered the Bajoran wormhole. (DS9: "By Inferno's Light")