Modern Freaking: Pull Phone Numbers From YouTube Audio

[Charlie X-Ray] is having some modern fun with the phone system by pulling dialed numbers from the audio track of YouTube videos (translated). The first step was to find a video where a telephone is being dialed and the sounds of the keypresses are audible. You can’t tell those tones apart, but a computer can. That’s because each number pressed generates a combination of two out of seven closely related frequencies. [Charlie] isolated the audio using Audacity, then wrote a python script to generate a spectrogram like the one above. By matching up the two dark nodes you can establish which two frequencies were played and decode the phone number being dialed. So how does this work again… find audio of a phone being dialed, decode the number.. profit?

48 thoughts on “Modern Freaking: Pull Phone Numbers From YouTube Audio

  1. This isn’t exactly anything new, frankly if there’s little background noise you could hold a phone (with a dialtone) up to the speaker and it would dial the number. Or just use a dedicated DTMF decoder IC (they cost pence/cents)?

  2. Reminds me of Three Days of the Condor, 1975:

    “G. Carriage Return. Symbol for Number”

    He plays a recording of tones into a phone, presumably to an operator or computer with speech recognition, and receives back the number of the assassin, Jobert.

  3. @Nich: No, even if you have an antique dial pulse phone, the tones are decoded by your local phone company.

    As for preaking uses, this kind of stuff can be used to steal voice mail and other access codes, although I doubt you’ll pick up much of that from youtube videos.

  4. If you hold the microphone of an analog phone to your computer speakers and then play the clip, the number will be dialed. You wouldn’t know what number is being dialed but you would get connected to the number :) It’s the same way blue boxes used to work back in the phreaking days.

  5. You can decode the bit-stream header and adjust it too on off-audio. I seen this done when ‘vlogging’ first came around to pwn people..

    Also..isn’t hak5 to hacking culture what MTV is to the music industry? None of the people on there actually have talent. It’s produced media backed by multiple marketing companies.

  6. Interesting, but any tone decoder chip could do this too. I mean, after all, that’s how it’s been done in the past. This is just a more technological way of doing the same thing.

    I guess it does get rid of external components.

    But I’m not sure why you’d want to do this anyway. Are there phone numbers in youtube that I should be really interested in to start with? I don’t recall ANY dialing in any of the video’s I’ve seen. Who are they calling that I should be interested in??

  7. @George J: The only time I’ve seen people dialling in a youtube video is for prank calls. Most of these pranksters seem to use Skype which I believe doesn’t use true DTMF but instead a single emulated (if you like) tone that is the same for each number.

    Is there much practical use for this? Not likely. Is it pretty clever anyway? Yes, I think so :)

  8. if they’re dialing their friends/family with a cellphone, you’re probably not going to hear anything since they’ll be in the phonebook. and idk why you’d make phreaking an F-word

  9. @mungwell as does Cool Edit Pro with DTMF generation to compare. This is basic stuff most of us have done years ago minus the youtube part. There are also a number of decoders from those days he would probably find helpful if ya can get dosbox to run them ;) Glad to see the new generation is trying tho :)

  10. Ummmm, ever heard of a DTMF decoder IC? This has been done a thousand times over, without the need for a computer.

    This is not “Preaking”. I am assuming that’s what you meant when you said “freaking”. This site is so pathetic. Wow.

  11. @matt,
    That’s real phreaking, HaD is only interested in “freaking” on youtube. I’m guessing from the title that mike is just looking for girls dancing in a risque fashion rather than hacking.

  12. Must add, :) i used to have an old school phone that had an actual bell. very fun. but using the phone base to dial numbers is very possible (hitting the hang up thing with the proper timing) but i dont recomend it. dialing 911 on accident is a biatch.
    I still think it is a good skill to know for phreaking.

  13. Phreaking (not freaking) is not dead!

    This isn’t a new trick. You can always just grab DTMF decoder software. You might have to mess around with some audio filters on ‘Adobe Audition’ but should generally work.

    Been doing it for a while.


  14. Did anyone else think of “Hey Arnold!” when they read this? There was an episode where Gerald took a video recording of someone dialing a phone and got the phone number from it.

  15. So many of you guys are really being ignorant…

    I mean, its a nice suggestion to use a decoder chip and some of you are genuinely being helpful by letting us know that they exist, but some of you seem to have a tone that using a decoder chip is easier because a computer isn’t involved, and that somehow this project is dumb because of that…

    Before you go and call someone else or their project stupid, why don’t you think about what you’re saying? This is a project to decode tones from videos on YouTube… And where there’s YouTube access, there’s always a computer (well, unless you’re using a smartphone, but thats not whats happening here).

    So which is easier? Buying a dedicated IC and programming a microcontroller (from your PC, no less) to decode the tones, or just doing it straight from the PC that accessed the video in the first place?

    I know some problems can be solved with $2 worth of hardware, but if you have a $1000 piece of hardware lying around that will already do it, there’s nothing wrong with using that…

    Really some of you don’t even think about your comments.

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