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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.

1. The ominous one

2. The one with the art history

3. The one with the confusing metaphor

4. The one for sports fans

5. The festive one

6. The one with the tight trousers

7. The one with someone who doesn't even know what security is

8. The one with the more obvious metaphor

9. The one with the bad trip

10. The psychedelic one

11. The one that brings you down to earth

12. The one with the eager ear