dubok

plural duboks

1. espionageA dead drop.

   His couriers should communicate with him through duboks – hiding places where messages could be left or collected, also called 'dead letterboxes' […]

   2011, Chapman Pincher, Treachery: Betrayals, Blunders and Cover-Ups

   3 more examples

   And then there are the duboks. Every Red Army intelligence agent abroad is assigned the task of finding duboks in the city where he is stationed. A dubok is a hiding place for anything that may be exchanged in espionage work […]

   1947, Hearst's International Combined with Cosmopolitan

   Meantime, in addition to the active agents, scores of others wait expectantly, always on the alert; scores of yavkas operate; scores of duboks are maintained; exchange of personnel goes on constantly.

   1955, David J. Dallin, Soviet Espionage, page 509

   […] was unable to remember the spy's cover name but he did not attach much importance to this, since, as he pointed out, cover names, like duboks, were changed from time to time.

   1981, H. Montgomery Hyde, The Atom Bomb Spies, page 91