The TRMC hackers spent the Winter of 1960-61 mapping the “Telephone Network Fingerprinting”, charting all of the places that MIT’s system tie lines were capable of reaching. The system was not connected to general phone lines but instead could take you to Lincoln Lab and from there to defense contractors across the country. From there it was a simple matter of trial and error. You would begin with an access code and add different digits to see who would answer. Once you knew where they were you could alternate the number to one up or one down to jump to the next line, courtesy of the unsuspecting phone company. Kotok: “If there was some design flaw in the phone system such that one could get calls that weren’t intended to get through, I wasn’t above doing that, but it was their problem, not mine.”
While certainly unethical, his intentions were simply for exploration and nothing malicious. However, some outsiders such as Sampson’s roommates could not comprehend this. They thought it was alright to exploit the system bugs for fraudulent purposes rather than some “holy justification” of exploration. After pressuring Sampson for several days, he gave in and handed them a number that could reach an “exotic location”. He told them “you can dial this from the hall phone but I don’t want to be around”. As they frantically went over to the phone to test the number, Sampson walked to the phone downstairs which began to ring. With a more official voice, he answered “This it the Pentagon, what is your security clearance, please?” Through it he heard the terrified gasps of his roommates as they quickly hug up.
It goes to show you that you should avoid pressuring people into helping you do that is wrong, especially someone as clever as Sampson. While the phone exploration was fascinating, Kotok had his sights focused on a different task. The PDP-1 was a brand-new computer designed by Digital Equipment Corporation (DEC) about to enter the world of MIT. The DEC people seemed to take notice of the freewheeling, interactive, improvisational, hands-on-Uber-alles style of the TX-0 community. The PDP-1 would help reinforce this behavior.