The FSB said the stone was being used as a high-tech
version of the spy's traditional letter-box or dead drop in which
agents can anonymously deliver or retrieve
information.
source
The rock allegedly contained equipment able both to receive and
transmit information, the officer said. "This was absolutely new
spy technology."
Rossiya television said that throughout last autumn Russian
informants would communicate by passing near the stone and
transmitting from a pocket personal computer. Days later, a British
diplomat would allegedly visit the stone and access the same
system.
