Phreaking is a slang term coined to describe the activity of a culture of people who study, experiment with, or explore telecommunication systems, such as equipment and systems connected to public telephone networks. The term phreak is a sensational spelling of the word freak with the ph- from phone, and may also refer to the use of various audio frequencies to manipulate a phone system. Phreak, phreaker, or phone phreak are names used for and by individuals who participate in phreaking. The term first referred to groups who had reverse engineered the system of tones used to route long-distance calls in the 1960s. By re-creating the signaling tones, phreaks could switch calls from the phone handset while avoiding long-distance calling charges which were common then. These fees could be significant, depending on the time, duration and destination of the call. To ease the creation of the routing tones, electronic tone generators known as blue boxes became a staple of the phreaker community. This community included future Apple Inc. co-founders Steve Jobs and Steve Wozniak. The blue box era came to an end with the ever-increasing use of digital telephone networks which allowed telecommunication companies to discontinue the use of in-band signaling for call routing purposes. Instead, telecom companies began employing common-channel signaling (CCS), through which dialing information was sent on a separate channel that was inaccessible to the telecom customer. By the 1980s, most of the public switched telephone network (PSTN) in the US and Western Europe had adopted the SS7 system which uses out-of-band signaling for call control (and which is still in use to this day), therefore rendering blue boxes obsolete. Phreaking has since become closely linked with computer hacking.
History Phreaking began in the 1960s when it was discovered that certain whistles could replicate the 2600 Hz pitch used in phone signalling systems in the United States. Phone phreaks experimented with dialing around the telephone network to understand how the phone system worked, engaging in activities such as listening to the pattern of tones to figure out how calls were routed, reading obscure telephone company technical journals (often obtained through dumpster diving), social engineering, building electronic devices called blue boxes, black boxes, and red boxes to help them explore the network and make free phone calls, hanging out on early conference call circuits and "loop arounds" to communicate with one another and writing their own newsletters to spread information. Phreaking was especially prevalent in universities, where it began spreading much like computer hacking would in the following decades. Before 1984, long-distance telephone calls were a premium item in the United States, with strict regulations. In some locations, calling across the street counted as long distance. To report that a phone call was long-distance meant an elevated importance because the calling party is paying by the minute to speak to the called party. Some phreaking consists of techniques to evade long-distance charges, which is criminalized as "toll fraud". In 1990, the pager cloning technique arose and was used by law enforcement. In the UK the situation was rather different due to the difference in technology between the American and British systems, the main difference being the absence of tone dialing and signaling, particularly in the 1950s and 1960s. Still, US and UK phreaking often reflected a shared culture. The tone system in the United States has been almost entirely replaced, but in some countries, in addition to new systems, the tone system is still available, for example in Italy.
Switch hook and tone dialer Possibly one of the first phreaking methods was switch-hooking, which allows placing calls from a phone where the rotary dial or keypad has been disabled by a key lock or other means to prevent unauthorized calls from that phone. It is done by rapidly pressing and releasing the switch hook to open and close the subscriber circuit, simulating the pulses generated by the rotary dial. Even most current telephone exchanges support this method, as they need to be backward compatible with old subscriber hardware. By rapidly clicking the hook for a variable number of times at roughly 5 to 10 clicks per second, separated by intervals of roughly one second, the caller can dial numbers as if they were using the rotary dial. The pulse counter in the exchange counts the pulses or clicks and interprets them in two possible ways. Depending on continent and country, one click with a following interval can be either "one" or "zero" and subsequent clicks before the interval are additively counted. This renders ten consecutive clicks being either "zero" or "nine", respectively. Some exchanges allow using additional clicks for special controls, but numbers 0-9 now fall in one of these two standards. One special code, "flash", is a very short single click, possible but hard to simulate. Back in the day of rotary dial, technically identical phone sets were marketed in multiple areas of the world, only with plugs matched by country and the dials being bezeled with the local standard numbers. Such key-locked telephones, if wired to a modern DTMF capable exchange, can also be exploited by a tone dialer that generates the DTMF tones used by modern keypad units. These signals are now very uniformly standardized worldwide. It is notable that the two methods can be combined: Even if the exchange does not support DTMF, the key lock can be circumvented by switch-hooking, and the tone dialer can be then used to operate automated DTMF controlled services that can not be used with rotary dial.
2600 hertz
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