A call detail record, also known as call data record, is a data record produced by a telephone
exchange or other telecommunications equipment that contains attributes that are specific
to a single instance of a phone call or other communication transaction that was handled
by that facility or device. It is the automated equivalent of the paper toll tickets that
were written and timed by operators for long-distance calls in a manual telephone exchange.
CDR Contents A call detail record contains metadata – that
is, data about data – containing data fields that describe a specific instance of a telecommunication
transaction, but does not include the content of that transaction. By way of simplistic
example, a call detail record describing a particular phone call might include the phone
numbers of both the calling and receiving parties, the start time, and duration of that
call. In actual modern practice, call detail records are much more detailed, and contain
attributes such as: the phone number of the subscriber originating
the call the phone number receiving the call
the starting time of the call the call duration
the billing phone number that is charged for the call
the identification of the telephone exchange or equipment writing the record
a unique sequence number identifying the record additional digits on the called number used
to route or charge the call the disposition or the results of the call,
indicating, for example, whether or not the call was connected
the route by which the call entered the exchange the route by which the call left the exchange
call type any fault condition encountered
Each exchange manufacturer decides which information is emitted on the tickets and how it is formatted.
Examples: Send the timestamp of the end of call instead
of duration Voice-only machines may not send call type
Some small PBX does not send the calling party In some corporate Private branch exchange
systems, a call detail record is termed a station messaging detail record.
Uses Call detail records serve a variety of functions.
For telephone service providers, they are critical to the production of revenue, in
that they provide the basis for the generation of telephone bills. For law enforcement, call
detail records provide a wealth of information that can help to identify suspects, in that
they can reveal details as to an individual's relationships with associates, communication
and behavior patterns, and even location data that can establish the whereabouts of an individual
during the entirety of the call. For companies with PBX telephone systems, call detail records
provide a means of tracking long-distance access, can monitor telephone usage by department
or office, and can create listing of incoming and outgoing calls.
Privacy The U.S. Supreme Court has held the records
of numbers called are not protected by the Fourth Amendment to the Constitution of the
United States because the caller "voluntarily conveyed numerical information to the telephone
company." But there is limited protection under the Electronic Communications Privacy
Act. See pen register for details. The revelation that call metadata records are being universally
collected and stored in the U.S. and elsewhere has generated considerable controversy. See
2013 mass surveillance disclosures. In June 2013, a top secret order of the United
States Foreign Intelligence Surveillance Court was leaked to the public. That order referenced
and defined call detail records as follows:
"IT IS HEREBY ORDERED that, the Custodian of Records shall produce to the National Security
Agency upon service of this Order, and continue production on an ongoing daily basis thereafter
for the duration of this Order, unless ordered by the Court, an electronic copy of the following
tangible things: all call detail records or "telephony metadata" created by Verizon for
communications between the United States and abroad; or wholly within the United States,
including local telephone calls.... "Telephony metadata includes comprehensive
communications routing information, including but not limited to session identifying information
number, International Mobile station Equipment Identity number, etc.), trunk identifier,
telephone calling card numbers, and time and duration of call. Telephony metadata does
not include the substantive content of any communication, as defined by 18 U.S.C. § 2510(8),
or the name, address, or financial information of a subscriber or customer."
See also Customer proprietary network information
NSA call database Telecommunications data retention
Pen register Internet Protocol Detail Record
Communications data Datacom
Average call duration Answer/seizure ratio
References
External links Visualize/playback 6-months' Call Detail Records
– records of German politician Malte Spitz