Thread drift question: how common are successful hacking (old definition of the word "hack") attempts against MIT's 5ESS? When I was at the 'tute long ago it had a SxS (in building 10 IIRC) with the main number at UN4-6900, and one of the popular entertainments among the student body was trying to find a live wire pair from which one could dial "9" to make an outside call [*]. Occasionally someone would manage to get into the switchroom and do a bit of rewiring, although I don't recall ever hearing of any damage being done other than a few unauthorized LD calls. (But one of the hackers' exploits in 1961 or so was described in an article in Newsweek ... not for his "informal" rewiring jobs, but for his use of what today is called "social engineering" to make an international call from a campus-only line.)
I'm having trouble imagining today's MIT students being able to resist the challenge of hacking into the switch and making it do "interesting" things.
There were other PABX systems on campus not connected to the "real" phone system. The dorms had their own SxS plant (and a manual board in East Campus, being converted to an automated plant as I left), and of course the TMRC folk had a SxS exchange built into the model train control system along with a lot of other WECo switchgear that somehow found its way to building 20.
[*] which resulted in an entry in the TMRC Dictionary: 9th Level, the: A level of communication attained most eminently by L. van BeethovenJoe Morris