(Isaac Grover) wrote in
om:

My initial goal is to capture the audio off the line and reconstruct
the audio into actual data that could be interpreted by me visually
with a hex editor.

It's just an analog audio signal of limited bandwidth -- not the sort of
thing that will be of much interest. However, if that's what you want,
just sample the analog stream with your PC sound card and store it to disk
(the soundcard will perform the required A/D conversion). There are many
tools (like Cooledit) that will allow you to examine and manipulate audio
data.

I'm interested in taking apart the data stream
that is sent to and from the CLEC.

What data stream? When you dial, you send a sequence of pulses or tones
(depending on your phone) to the local office . Once connected, you
send/receive analog voice signals. There is no "data stream" (or bits) to
be taken apart -- just an amplified audio signal from the telephone's
mouthpiece.

My final goal is to attempt to
inject/alter data in the outgoing stream, like altering the Caller ID
info, for example. It's just an intellectual challenge at this point,
and I'm not even sure it can be done.

Caller ID info isn't sent from your telephone, so you can't possibly alter
it. And if you don't pay for the service, your telco won't send any caller
ID to your phone either. If you do have caller ID, here is a FAQ that
describes the protocol:
http://www.repairfaq.org/filipg/LINK/F_CallerID.html

Murray Peterson wrote in message ...
What data stream? When you dial, you send a sequence of pulses or tones
(depending on your phone) to the local office . Once connected, you
send/receive analog voice signals. There is no "data stream" (or bits) to
be taken apart -- just an amplified audio signal from the telephone's
mouthpiece.

After being enlightened by you and others in this group, I'm wondering
if my project idea is going to be an exercise in futility.

Here's what I want to do, to see if/how it can be done. If you're a
data network geek, you can use programs like tcpdump, ethereal, etc.
to capture the data stream from a network route, apply filtering, and
reconstruct the data stream into something that can be read by
(trained) humans.

Is it possible to have a PC running any OS with say, dual modems, to
capture the audio stream from a phone line, filter whether it's a
voice or data call, and reconstuct the voice calls into wav files or
data calls into binary files? Yes, I realize that you can do this
much simpler with tape recorders and microphones, but my interest in
this project lies with the assumption that I do *not* have access to
the handset.

It's either possible, or the government has a handful of paranoid
maniacs convinced that the government is listening in to every phone
call everyone makes. I'm starting to think that the latter is more
plausible. =)

Isaac

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(Isaac Grover) wrote in
om:

After being enlightened by you and others in this group, I'm wondering
if my project idea is going to be an exercise in futility.

Very futile. The only phone line that it is legal to listen to is your
own, and there are even provisos about that. And you already know exactly
what is being sent over your own phone line.

Here's what I want to do, to see if/how it can be done. If you're a
data network geek, you can use programs like tcpdump, ethereal, etc.
to capture the data stream from a network route, apply filtering, and
reconstruct the data stream into something that can be read by
(trained) humans.

Phone systems consist of many types of "lines" -- the low bandwidth line
going from your home to the local office uses one of many protocols (POTS),
but there are also DSL and ADSL lines. Once you get into the phone system
itself, there are various protocols for passing this data around the system
(e.g. look up SS7 protocol).

Is it possible to have a PC running any OS with say, dual modems, to
capture the audio stream from a phone line, filter whether it's a
voice or data call, and reconstuct the voice calls into wav files or
data calls into binary files?

Yes, but only in a very nebulous sort of way. Voice calls are easy --
just run them into your sound card and have it record the data to a wav
or mp3 file. There are many programs around that do exactly this (phone
answering/messaging done by your PC and a cheap modem). Binary data can be
recognized and decoded, but you will need a modem that uses the same
protocol as the sending modem. There are a *lot* of different modem
protocols, although most modems can deal with the various standard
protocols. This is not something you ever want to attempt via software --
it's possible, but I doubt you would live long enough to write all of the
required software.

Yes, I realize that you can do this
much simpler with tape recorders and microphones, but my interest in
this project lies with the assumption that I do *not* have access to
the handset.

Go out and buy something like this: www.dynametric.com/call_saver.asp
That gets the data off your phone line onto your PC -- everything after
that is up to you. Be sure to first look up the laws applying to recording
of telephone conversations.

It's either possible, or the government has a handful of paranoid
maniacs convinced that the government is listening in to every phone
call everyone makes. I'm starting to think that the latter is more
plausible. =)

Government resources far outstrip anything you could hope to do by
yourself. For one thing, they don't need to tap into your local line --
they only require that a copy of the SS7 data packets get sent their way.
They can also afford a bank of every modem type known for decoding of data
transmissions, and some seriously high-end voice recognition software to
listen for "interesting" keywords. None of this is within the reach of a
single individual -- especially access to telephone data other than your
own.

I'll repeat this, just in case you missed it above -- you already know
exactly what is being sent over your own local phone line, and that's the
only line to which you have legal access. In other words, you are going to
spend a lot of time to "analyse" a data stream that holds no mysteries
whatsoever.