[JanneVee]

I read about this in the Silence on the Wire by Michal Zalewski. And you don't need a fullblown AI, a good statistical model is enough to make a guess on passwords, and if you have a bunch of probabilities to cut down your search space to a more probable set. And the book is from 2005, so I wouldn't say it is new. https://nostarch.com/silence.htm

I even remember reading about how Clifford Stoll recognized the different attackers by "typing rhythm" in Cuckoo's Egg.

[hprotagonist]

“fist recognition” is at least as old as morse code.

https://en.wikipedia.org/wiki/Keystroke_dynamics

[flir]

Earliest reference I know is to a TLA bugging plaintext teletype printers in The Hacker's Handbook, Hugo Cornwall, 1985.