To review, topics I have covered were
1876 - First case of telecom related fraud - seems that Bell did not invent the phone, but that the man who did could not afford to patent it.
1889 - First denial of service (DoS) and crime _ see below.
1903- The first telecom hacking - Marconi's demonstration and "secure" service were interrupted and listened to.
First Denial of Service (DoS) and crime
The story goes that Amon Strowger, a St. Louis undertaker, became upset on finding that the wife of a competitor was a telephone operator at the local (manual) telephone exchange who made his line busy and transferred calls whenever a caller asked to be put through to Strowger, the calls were deliberately put through to his competitor, her husband.(1)(2)
"Necessity is the mother of invention" so Strowger developed the dial telephone system to get the operator out of the system. (1)
Now if you think about it, this was both a DoS attack, as the wife blocked calls to Mr. Strowger's company and to make it worse she illegally redirected those calls to a competitor.
(1) Bill's 200-Year Condensed History of Telecommunications at http://www.cclab.com/billhist.htm
(2) Theory of Electromechanical Switching at http://www.seg.co.uk/telecomm/automat1.htm