“Secrets of the Little Blue Box: A Story so Incredible It May Even Make You Feel Sorry for the Phone Company”, Ron Rosenbaum1971-10-01 (computer security)⁠:

[Early account of “phone phreakers” and their most famous hacking device, the blue box, used to control the Bell Phone System and enable free long-distance calls (then exorbitantly expensive); the blue box was famously based on an AT&T research paper describing the tone frequencies and how they control the phone switching system. The author hangs out with phreaks such as Captain Crunch to see how it all works.

After reading Rosenbaum’s article, Steve Jobs and his partner in founding Apple, Steve Wozniak, “collaborated on building and selling blue boxes, devices that were widely used for making free—and illegal—phone calls. They raised a total of $29,134.45^$6,000₁₉₇₁ from the effort.”]