feed the hydra
The process of documenting networks of gossips, often at an office or at school, by feeding distinctive, false statements to different members of the network and then listening for references to those statements made by other members of the network.
"Nicholas never had thought to take up the game himself, to feed the hydra false information that wold echo in the whispering of its many heads" — John Fowles, "The Magus"
feeding the hydra
A technique used by intelligence agencies to uproot spies by feeding them phony information, then documenting their response to it. Also used by attorneys, and others, to reveal breaches of confidentiality.
As soon as we began to suspect Vincent was leaking information to the Nazis, we responded by feeding the hydra, and the Nazis responded as you would predict.