WikiLeaks says the CIA is going all the way back to 1992.
Naked Security explains:
Remember those 1990s MS-DOS computer games that had a “Boss” key?
You could only run one application at a time back then, so if someone came past while you were playing the game on work time you needed a quick way to pop up a fake business app – usually a stripped down spreadsheet program – to act as your “cover story” so you wouldn’t get caught.
(Yes, you recognised it correctly: the Boss screen above is from the original Tetris.)
Fast forward 25 years, and recent revelations from Wikileaks suggest that the CIA has its own modern take on the Boss key.
Apparently, the CIA maintained a list of plausible “cover story” apps that it recommended for field agents who would be working inside a target organisation.