Phreaking, fraudulent manipulation of telephone signaling in order to make free phone calls. Phreaking involved reverse engineering the spec
"John Draper, a friend of Engressia, discovered that a whistle distributed as a prize in Captain Crunch cereal emitted a perfect 2,600 MHz pitch, thus earning him the moniker “Captain Crunch.” As phreaking evolved, the use of what was known as a blue box, or Mfer, became the most-common way of manipulating the phone signal."










