mitting a sound that could be misconstrued as a dialing tone. There was, therefore, no reason to use DTMF dialing-instead, trunk sig- naling was performed using single frequency tones. Specifically, if a switch wished to seize a long-distance trunk, it issued a single-frequency 2,600 Hz tone, which would signal the seizure to take place. Once the trunk seizure had occurred, the dialed digits could be outpulsed and the call would proceed as planned. In 1972, John Draper, better known by his hacker name "Captain Crunch," determined that the toy plastic bosun's whistle that came packed in boxes of Cap'n Crunch cereal emitted-you guessed it-2600 Hz. Anyone who knew this could steal long-distance service from AT&T by blowing the whistle at the appropriate time during call setup. Before long, word of this capability became common knowledge and Cap'n Crunch cereal became the breakfast food of choice for hackers all over the country. Soon hackers everywhere were constructing "blue boxes," small oscil- lators built from cheap parts that would emit 2,600 Hz and make possi- ble the kind of access that Draper and his cohorts were engaged in. In fact, Steve Wozniak and Steve Jobs, both founders of Apple, were early blue box users and, according to legend, used the money they made build- ing blue boxes to fund the company that became Apple. Draper, a highly skilled hacker, was eventually caught and prosecuted for his activities, but he was given work furlough and was able to con- tinue his software design studies. He is now a successful intrusion detec- tion software designer! Returning to our example again, then, let's retrace our steps. Cristina dials Adam's number. The call travels over the local loop, across aerial and/or underground facilities, and enters the central office via the cable vault. From the cable vault the call travels up to the main distribution frame and then on to the switch. The number is received by the switch in Cristina's serving central office, which performs an SS7 database lookup to determine the pr