Kevin McDonaldJun 18, 2025

Long before the internet, some phone networks were hackable by playing a single tone at 2600Hz.

Whistled into a phone, it could grant you unrestricted access. Do you have the vocal chops to be an old-school phone phreak?

I built a web app to test your ability to produce the legendary frequency. You won't get free long distance calls but you will get some honor in the knowledge that you could have been a cool hacker. 😎

I am sad to say that I can only whistle up to 1100Hz... But my wife (a long time woodwind player) is able to consistently get it.

Give it a try: https://phreak.kmcd.dev/

#phreaking #2600Hz #bluebox #RetroComputing #hacker #infosec #Tech

Phone Phreak Emulator

Test your phreaking skills by hacking this phone line.

Show threadIan K TindaleJun 18, 2025
@sudorandom when was this ever true? The earliest phones I remember in the 1960s used carbon microphones but had no awareness of tones anywhere in the system, at least from the GPO phone in the hallway by the door. You could dial by imitating clicks by pressing the hook in and out several times, but there was absolutely nothing to do with tones about a phone.
Show threadKevin McDonaldJun 18, 2025

@u0421793 Source: https://en.wikipedia.org/wiki/Phreaking#History.

Indeed, this did happen in the 1960s from what I read. I believe this came about "Touch tone" era of telephony, where tones were indeed used to input number input and special tones were used for control systems. It's my understanding that it was new shiny at the time because yes, rotary phones would indeed disconnect and connect the line in order to input numbers. Tone tone would eventually replaced that system.

Phreaking - Wikipedia

Show threadIan K TindaleJun 18, 2025
@sudorandom no, push button DTMF phones didn’t exist back then – they were to come in in the early-middle 80s – but you couldn’t just whistle a tone into them, that’d be insane, it was dual-tones multi-frequency, but none of the frequencies are what you describe, and anyway you’d need to generate two frequencies at once, differently per key
Show threadKevin McDonald

@u0421793 bro, I'm reading this from reputable sources. Certain phone routes were vulnerable to a single 2600 tone. Phreaking is said to have begun with the discovery of this exact SINGLE 2600Hz tone.

I agree that the most common signalling mechanism was dual tone but that's not as fun since extremely few people can do that with their voice. And yes, this is why blue boxes exist.

Jun 18, 2025 at 11:43amWeb
Show threadStuck HereJun 18, 2025

@sudorandom @u0421793

There's a couple of documentaries on Capt Crunch and the other hackers who discovered all of this.

Research phone freaks. It's incredible.

Show threadIan K TindaleJun 18, 2025
@MyWoolyMastadon @sudorandom quite what ‘capt crunch’ actually is is beyond explanation, I’ve never heard of that
Show threadStuck HereJun 18, 2025

@u0421793 @sudorandom

Yep. The toy whistle in the cereal was removed once Ma Bell figured out what was happening.

If memory serves from the documentary about the phone freaks they held competitions.

Ahem, even Jobs & Woziak made an electronic device to mimic tones that allowed people to make free long distance calls. It's in the Jobs biography.

Show threadIan K TindaleJun 18, 2025
@MyWoolyMastadon @sudorandom hang on – what cereal, nobody’s mentioned a cereal yet, what on earth are you talking about.

What on earth is ‘Ma Bell’.

None of this is making any sense.
Show threadPanicky_PatzerJun 18, 2025
@u0421793 Cap'n Crunch is the name of an American cereal marketed toward children that came with a "prize" of a child's whistle inside. Apparently, it could create a specific tone that would allow someone to access certain blocked services when played through a telephone receiver. At the time, the American Bell Telephone Company--referred to as "Mama Bell" or "Ma Bell" for short, probably because of their monopolistic business practices--was unhappy about this.
Show threadnarpolepticJun 18, 2025

@u0421793 @MyWoolyMastadon @sudorandom Ian, you appear to be assuming that UK-local context is applicable worldwide. For this conversation at least, it is not

Ma Bell = the Bell Telephony family of service providers that used to exist in the USA.
Capt Crunch refers to a promotion that the cereal ran where customers could get a free whistle that allegedly emitted a 2600Hz tone that could be used to get free phone service. This all happened 4 or 5 decades ago. See also https://en.m.wikipedia.org/wiki/2600_hertz.

2600 hertz - Wikipedia

Show threadStuck HereJun 18, 2025

@narpoleptic @u0421793 @sudorandom

What's truly weird is that Jobs & Wozniak dabbled in phone freaking and made money selling a device that mobsters used to circumvent federal agents.

https://www.chaintech.network/blog/a-journey-from-1955-to-1980-the-intriguing-world-of-phone-phreaks/

The Shocking Tale of Phone Phreaks: 1955-1980 Odyssey

Who were Phone Phreaks? And how did they change the course of history of cybersecurity? Uncover this fascinating tale in our insightful blog.

Chaintech
Show threadnarpolepticJun 18, 2025
@MyWoolyMastadon @u0421793 @sudorandom oh, I didn't know about the Woz/Jobs bluebox - thanks for the link, I look forward to reading more about it 🙂
Show threadStuck HereJun 18, 2025

@narpoleptic @u0421793 @sudorandom

Grab a copy of the Jobs biography. There's a bit in there about it. It's the chapter in which Jobs & Wozniak meet. It's surreal to think how Jobs used Wozniak and did some shady stuff long before the first Apple Computer.

Show threadIan K TindaleJun 18, 2025
@MyWoolyMastadon @narpoleptic @sudorandom I read it, in the 80s – I remember that bit, I didn’t relate to it at all as it completely contradicted how an actual telephone network works in my experience, so I put it down to just fictional bravado making themselves sound cool, but now I realise it is because they were in a foreign country so things were different for them
Show threadMarty FoutsJun 18, 2025

@u0421793 @MyWoolyMastadon @narpoleptic @sudorandom Part of the problem is that your understanding of how the phone system works appears to be limited to the user interface but does not seem to include how the system works internally.

Non US systems also automated long distance routing using tones for in band signals. The frequency wasn’t 2600hz, but it would work the same way.
Even in the 60s.

Show threadStuck HereJun 18, 2025

@u0421793 @sudorandom

Before the big telecommunications break up Ma-Bell or Bell Telephone controlled the phone industry in the USA. Plus they owned the equipment in your home that you paid rent to use. You could never own it. https://www.u-s-history.com/pages/h1803.html

As to cereal, it was a toy whistle given away in Captain Crunch cereal that sparked an explosion in phone freaks. The whistle gave the exact tone needed for free long distance. https://phreaknet.org/phreak/

Bell Telephone System

Show threadOriel Jutty Jun 18, 2025

@u0421793 @MyWoolyMastadon @sudorandom

hang on – what cereal, nobody’s mentioned a cereal yet, what on earth are you talking about.

Kevin has mentioned it, indirectly, in the Wikipedia link he gave you. It literally says: "John Draper discovered through his friendship with Engressia that the free whistles given out in Cap'n Crunch cereal boxes also produced a 2600 Hz tone when blown (providing his nickname, "Captain Crunch")."

As for when and where this happened, the very first sentence of the linked section states: "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."

Show threadThomas Lee ✅ Jun 20, 2025
@u0421793 @MyWoolyMastadon @sudorandom Captain Crunch was an American breakfast cereal for kids. Loaded with sugar and other crap. The packages contained a toy, one of which was a whistle. This whistle blew at precisely 2600.
Show threadMarty FoutsJun 18, 2025
@u0421793 @MyWoolyMastadon @sudorandom “Cap’n Crunch” was a US cereal that gave away a toy whistle in the box of cereal. Turns out the whistle is supposed to have generated the correct (2600 hz) signal to trigger the in band signal to initiate a long distance call without generating any billing, in effect, free long distance b
Show threadIan K TindaleJun 18, 2025
@sudorandom no, this has never ever been possible – you’re probably talking about some highly local scenario in some foreign country somewhere far away which had different technology, but seriously, this was not the lived experience of any normal person anywhere around when I was growing up, those of us who had a phone at home (which wasn’t everybody) had a normal GPO telephone, which used clicks to dial. Later in the 80s deregulation came and the first DTMF phones arrived, some with green tags (allowed) and some naughty imported ones with red tags (not allowed) (why did they sell them then) and from that point on, people were also allowed to connect a modem directly to the (then-new) phone socket. Prior to that, it was only acoustic couplers allowed. But the acoustic coupler tones were not what you are describing, and didn’t interact with the normal GPO phone system.
Show threadOriel Jutty Jun 18, 2025
@u0421793 @sudorandom Cool. Tell that to Bell and the FBI: https://www.counterpunch.org/2008/06/30/blind-whistling-phreaks-and-the-fbi-s-historical-reliance-on-phone-tap-criminality/
Blind Whistling Phreaks and the FBI's Historical Reliance on Phone Tap Criminality

In 1971, Ron Rosenbaum’s Esquire article, “Secrets of the Little Blue Box”, introduced America to phone phreaks, a subterranean network of geek explorers

CounterPunch.org
Show threadOriel Jutty Jun 18, 2025
@u0421793 @sudorandom As for the "highly local scenario in some foreign country": Yes, the country in question being the USA.
Show threadFace ThumbJun 18, 2025
@barubary @u0421793 @sudorandom The USA is foreign to me :)
Show threadMarty FoutsJun 18, 2025
@sudorandom @u0421793 Y’all are talking past each other. The 2600 signal was internal in band and not generated by phones. Also it seems that there’s some confusion about the difference between US/AT&T versus other/GPO. they are similar but have different deployment history n