Long before it was at the centre of a huge spying scandal, the US National Security Agency had the communist threat to deal with - and wanted to make sure its staff did not spill secrets.
A vast archive of posters, apparently for display at the spy agency's offices, has been posted online thanks to a freedom-of-information request from governmentattic.org.
The website asked for "a digital/electronic copy of the NSA old security posters from the 1950s and 1960s", although confusingly it also got one featuring John Travolta.
Here are some of our favourites. The full, 139-page document, can be found here.
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