In 1942, the U.S. Office of War Information created a marketing slogan that has since become a favored colloquialism for the importance of secrecy:
Loose Lips Sink Ships.
Other than the rhyming, the government wasn’t actually trying to be clever with that campaign — idle talk to the wrong person could literally have sunk a ship in 1942.
But in 2017 — a year where so far the mainstream news has been more or less defined and dominated by a series of leaks, anonymous sources and unattributed tips — the phrase has enjoyed something of a comeback.