
Evan Doorbell's Classic Phreaking Tapes - fapjacks
http://www.evan-doorbell.com/production/
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cperciva
On the topic of phreaking, does anyone know if modern condo entryphone systems
are vulnerable? The fact that pressing a button on my phone unlocks the front
door to the building makes me wonder how it could possibly _not_ be vulnerable
to having the right pitches played, but I would hope that the dangers of in-
band signalling have been widely understood for long enough that systems would
be protected...

~~~
kkielhofner
I assume this is one of those systems where a potential entrant types a code,
and the systems calls a pre-provided number for the occupant of the unit who
provided the code to the entrant?

The common denominator on the PSTN is listening for inband DTMF within a G.711
"encoded" stream.

The "security" in this system is the condo entry phone device dialing out to
the PSTN (via some mechanism) to the destination number, which is routed via
SS7 to the proper owner.

This security mechanism is somewhat similar to those used by two-factor
systems that send SMS via SS7 to destination numbers. It's not without fault,
there have been many demonstrated attacks against the SS7 network.

~~~
cperciva
Sorry, I should have specified more. This is a "potential entrant selects the
person they're trying to visit; system phones the pre-programmed number for
that occupant; occupant talks to the visitor and presses a button to let them
in". In my building, I have to press 6 to make the door unlock.

Could a vistor play a very loud "touchtone phone 6" into the microphone and
make the system think that the occupant pressed that number?

~~~
mulmen
That would require the audio signal to be a single channel right? That or the
residents phone would have to be very loud. I'm not sure but I think phones
operate on a dual channel (tx/rx) setup which is what allows all participants
to talk simultaneously.

~~~
cperciva
I was thinking echoing. I don't know how loud a button tone needs to be for
the entryphone system to accept it as an instruction to unlock the door.

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dmix
This sounds interesting but he's using so much phone jargon it's hard for me
to follow. Is there some good intro to this stuff somewhere?

~~~
brianzelip
Sure, one is 'Exploding the Phone', 2013, by Phil Lapsley.
[http://explodingthephone.com](http://explodingthephone.com)

Great book.

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EvanAnderson
I very much enjoy the "Dom Tuffy" series (though I highly recommend all of Mr.
Doorbell's recordings-- his voice is pleasing and hearing how it has changed
over his life is amusing, if nothing else).

The August, 2001 tapes in Nantes, Quebec are especially poignant to me. I grew
up in a rural small town that had the analog phone switch replaced with a
digital switch (a DMS-10) in the late 1980's. A couple of other little towns
around still had analog switches into the early 90's. I "played around" with
them a little bit but really didn't understand the technology. Now I wish I'd
had more time with them.

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watmough
This is awesome:

[http://www.evan-doorbell.com/production/PanPulsLovers.mp3](http://www.evan-
doorbell.com/production/PanPulsLovers.mp3)

It covers the exchanges talking to each other.

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fapjacks
In particular, the "How Evan Doorbell became a Phone Phreak" series is
excellent storytelling with plenty of detail to keep hackers entertained.

~~~
mdp
Link the Soundcloud version, which might be easier for mobile listeners -
[https://soundcloud.com/evan-
doorbell/sets/group-1](https://soundcloud.com/evan-doorbell/sets/group-1)

~~~
hansjorg
This is really well produced, and he's a great narrator! Loving both the
hacker spirit and the contemporary music with DTMF mashups.

NPR or someone should pick this up and give it a broader audience.

~~~
riffic
Radiolab did a piece on Joybubbles -
[http://www.radiolab.org/story/187724-long-
distance/](http://www.radiolab.org/story/187724-long-distance/)

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pagnol
What exactly is this about?

~~~
ZenoArrow
Phreakers were/are telephone system hackers. Back in the day it was possible
to hack telephone systems using simple electronics and some technical
knowledge. The page being linked to seems to go into some of the history of
phone phreaking.

Incidentally, the following clip contains the most impressive demonstration of
phreaking I've ever seen, showing a blind phreaker with perfect pitch called
Joe Engressia who was able to hack the phone system just by whistling:

[https://www.youtube.com/watch?v=vVZm7I1CTBs](https://www.youtube.com/watch?v=vVZm7I1CTBs)

A fair amount of the hacker culture of the 80s and early 90s (hacker in terms
of what the common perception of a hacker is) seems to owe its debt to the
trail blazed by phreakers.

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flyinghamster
The "Sounds of Long Distance" series does a pretty good job of explaining how
the phone network was laid out in the waning years of the Bell System.

