Such a method of encoding stuff inside other file formats is as old as the computer industry.
As a matter of fact, in the past there were many contests where people had to try to "crack" the implemented messages in Word documents, GIF files, graphical data, etc... (I also once participated with one of those contests back in the 80's)
Thus, no this isn't simply a movie-thing. It actually exists and is "used" widely and information about this can be found on many sites around the web. (This method of encapsulating messages inside other "normal" formats has an actual name, but I forgot it
)...
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