Dead Drops Project

The dead drop spike is a concealment device similar to a microcache which has been used since the late 1960s to hide money, maps, documents, microfilm, and other items. The spike is waterproof and mildew-proof and can be shoved into the ground or placed in a shallow stream to be retrieved at a later time.
Modern dead drop techniques
On January 23, 2006, the Russian FSB accused Britain of using wireless dead drops concealed inside hollowed-out rocks to collect espionage information from agents in Russia. According to the Russian authorities, the agent delivering information would approach the rock and transmit data wirelessly into it from a hand-held device, and later his British handlers would pick up the stored data by similar means.