The Internet's Coldest Case
Manuel Cebrian's essay on "Markovian Parallax Denigrate" — hundreds of identically titled, meaningless posts that flooded Usenet in August 1996 and have never been explained. It walks through each theory in turn: a Cold War-style numbers station, a cipher, a mail-server fault, or an early Markov-chain text generator in the lineage of the Mark V. Shaney experiment, and what the trail of headers actually supports.
Why I recommend it: A enjoyable read, and a useful one: machine-generated nonsense has been circulating for thirty years, and this is a case study in how hard attribution is once it does. The author is careful to label what is evidence and what is speculation — which is more than most write-ups of it manage. Medium sometimes meters free reading, so tell me if it asks you to sign in.