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-o[ Defeating the Caller ID system ]o-
-o[ D4RKCYDE ]o-
-o[ by hybr1d <hybrid@dtmf.org> ]o----------------------------------------
-----BEGIN PGP SIGNED MESSAGE-----
Defeating The Caller ID System
With Simple but Effective Stealth.
July 1999.
hybrid (hybrid@dtmf.org)
(http://hybrid.dtmf.org)
quick disclaimer: I do not encourage any of the information provided in this
file. I, or f41th cannot be held responcerble for your use of the information
provided in this article, it has been provided for informational purposes
only.
(introduction)
CallerID (CID) or CND (Calling Number Delivery), is an extension to the
widley used ANI (Automatic Number Identification) system. The telcos use ANI
as a means for billing information when you make a toll-call, however dispite
what alot of people think, ANI is not used as part of the CID system, it was
the first system used to allow the recieving party know who was calling and
was widely used before the advent of the SS7 telephony protocol, but sinse
the implementation of SS7 CID/CND has become popular, both in residential
subscriber loops, and commercial lines. In this file I am going to show how
the CID/CND system works, specific to different *bell specifications aswell
as the differences in other countrys, such as the UK. Before we go any
further, you need to know the basics of the *bell CID protocol;
CID information (data) is transmitted on the subscriber loop using a method
known as FSK (Frequency Shift Keyed) modem tones. This data is transmitted in
ASCII format and contains the information needed to display the CID mesage at
the terminating line. The actual data burst occurs between the first and
second ring of the line, and contains basic information about the originating
point of the call, such as the date, time, and of course the calling number.
On more upto date systems, or in a local area, the name of the caller will be
displayed next to their number aswell. Further advances in CID include a new
system called CIDCW or (CID on Call Waiting), where the call waiting tone is
heard and the CID of the second calling person is exposed.
(definition)
As I said before, Caller ID is the identification of the originating
subscriber line. For example, say you had a line installed under your own
name, your details would be stored alongside your line information in your
telcos directory listings. So when you call someone with a CID unit that
displays the calling partys name, your name would be displayed alongside the
number, or whoever pays the bill for the line. Obviously the telco has no
real way of knowing just _who_ is making the call, so the term Caller ID
would be inapropriate, and should technically be refered to as Calling Number
Identification because it is the name of the person associate with the line
rental, and not your docs that are transmitted. The actual CID information is
transmitted to the terminating subscriber loop, as I said before, between
the first and second ring implementing a bell202 type modem specification.
There are 2 tones that are tranmitted, one of them contains the mark
transmission (logic 1) and the other contains the space transmmision (logic
0), mark and space. The transmitted message contains a channel seizure string
and then a mark string followed by the actual caller information. If the
recieving line only has basic CID information installed (where they only
recieve the date, time and number of the caller) SDMF (Single Data Message
Format) is used in the CID data burst. If however, the recieving person has
a more advanced version of CID where they can see the name of the person
calling, MDMF (Multiple Data Message Format) is used in the data burst. If
the MDMF method is used, and you have withheld your CID, the recieving line
will only see a message saying the information was blocked by the caller, or
is unavailable. Later I will discuss ways of making your line information
completly unavailable to the called party.
In New Jersey 1987, the firs