Back in nineteencanteen when I got my R/T licence, signing the Oficial Secrets Act was part of the paperwork. The wording was along the lines of, "Nothing heard on the frequency may be disclosed to a third party."
An Irish ex-colleague spent several months in a Belgian jail when found outside a NATO base witha VHF receiver, according to the prosecution it could have been converted to a transmitter and used to send information to Russia.
I said it to Wilbur and I said it to Orville, it'll never get of the ground.