"During the 1970's, the phone phreaks or phone hackers appeared: they learned ways to hack the telephonic system and make phone calls for free.

John Draper built a 'blue box' that could do this and the Esquire magazine published an article on how to build them. Fascinated by this discovery, two kids, Steve Wozniak and Steve Jobs, decided to sell these blue boxes, starting a business friendship which resulted in the founding of Apple.

Getting their laughs and skills from hacking and cracking into primitive computers and exploiting the Arpanet (predecessor to the internet), they created a novelty that would become the target of federal crackdown in years to come."
source

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related links:

timeline on history of computer hacking