@mattblaze AFAIK the only group to discover Ken’s hack was us in PWB/UNIX. One of the other guys noticed C prepreprocessor had gotten bigger, looked at binary namelist, found symbol not in source code. I got onto Ken’s system, found the code, very clever.

A bit latet, I was in Lab 127’s terminal room, talking to dmr or bwk, and overheard amusing conversation between ken and Robert Morris Sr, who sometimes consulted for NSA.
(RM Jr of worm fame was just a kid then.)

They were chortling away over cleverness of exploit. Then one (must have been ken) said “think we could put this over on NSA?” (which already had UNIX systems... we did favors now and then).
More chortling, then (must have been Bob): uhh, NSA really doesn’t have sense of humor.

PWB crew ran 1st real UNIX computer center & we were hyper-sensitive, partly because someone had called at night, told operator he was Ken Thompson & needed root password ... and got it. Turned out to be high schooler ... proving that social engineering tactics have been eternal.

Years later, as many BTL Directors were buying PDP11-70s for labs as general service systems, some PWB crew were asked to do security audits, given experience running biggest UNIX site. One lab was very proud of enhanced password software.
We did audit, agreed with that, BUT: