DEAD DROP

To minimize the risk involved in conducting personal meetings or engaging in potentially dangerous brush  contacts with agents, case officers may exchange information by means of an ostensibly innocuous site that both parties can visit without arousing suspicion. Complex tradecraft may require signals to be sent to indicate that a particular site has been selected and is ready to be serviced. Dead drops can range from convenient crevices in walls and matchboxes hooked behind radiators to carefully crafted items such as hollowed-out bricks, lumps of coal, and other natural-looking items adapted to conceal documents, microfilms, or cash.