Yes, the first thing I thought of was the “Canary Trap” that Tom Clancy described in “Patriot Games”.
(from Wikipedia)
The term was coined by Tom Clancy in his novel Patriot Games, although
Clancy did not invent the technique. The actual method (usually
referred to as a Barium meal test in espionage circles) has been used
by intelligence agencies for many years. The fictional character Jack
Ryan describes the technique he devised for identifying the sources of
leaked classified documents:" Each summary paragraph has six different versions, and the mixture
of those paragraphs is unique to each numbered copy of the paper.
There are over a thousand possible permutations, but only ninety-six
numbered copies of the actual document. The reason the summary
paragraphs are so lurid is to entice a reporter to quote them verbatim
in the public media. If he quotes something from two or three of those
paragraphs, we know which copy he saw and, therefore, who leaked it. "A refinement of this technique uses a thesaurus program to shuffle
through synonyms, thus making every copy of the document unique.
It seems to make a lot more sense in Clancy’s context than as a DRM tool.
