jungle telegraph

noun2

1. •
   A system used by primitive cultures in remote tropical regions for communication over long distances, such as drum sounds or a relay of runners.

   • Working both sides of the stream, they got native chieftains to pass the word by jungle telegraph. — 1958
2. •
   A gossip network; an informal communication system within a group or organization.

   • And the jungle telegraph at Bryant Park is alive with rumors that the show's biggest name, Lauren Conrad, will be here any day. — 2008