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 McDonaldJun 18, 2025

@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.

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 threadnarpoleptic

@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

Jun 18, 2025 at 1:26pmWeb
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.