A pen register, or dialed number recorder (DNR), is a device that records all
numbers
A number is a mathematical object used to count, measure, and label. The most basic examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers can ...
called from a particular
telephone
A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...
line.
The term has come to include any device or program that performs similar functions to an original pen register, including programs
monitoring Internet
The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
communications.
The United States statutes governing pen registers are codified unde
18 U.S.C., Chapter 206
Definitions

The term ''pen register'' originally referred to a device for recording
telegraph
Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas ...
signals on a strip of paper.
Samuel F. B. Morse's 1840 telegraph patent described such a register as consisting of a
lever
A lever is a simple machine consisting of a beam (structure), beam or rigid rod pivoted at a fixed hinge, or '':wikt:fulcrum, fulcrum''. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, l ...
holding an armature on one end, opposite an
electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets usually consist of wire (likely copper) wound into a electromagnetic coil, coil. A current through the wire creates a magnetic ...
, with a
fountain pen,
pencil
A pencil () is a writing or drawing implement with a solid pigment core in a protective casing that reduces the risk of core breakage and keeps it from marking the user's hand.
Pencils create marks by physical abrasion, leaving a trail of ...
or other marking instrument on the other end, and a clockwork mechanism to advance a paper recording tape under the marker.
The term ''telegraph register'' came to be a generic term for such a recording device in the later 19th century. Where the record was made in ink with a pen, the term ''pen register'' emerged. By the end of the 19th century, pen registers were widely used to record pulsed electrical signals in many contexts. For example, one fire-alarm system used a "double pen-register", and another used a "single or multiple pen register".
As
pulse dialing came into use for
telephone exchange
A telephone exchange, telephone switch, or central office is a central component of a telecommunications system in the public switched telephone network (PSTN) or in large enterprises. It facilitates the establishment of communication circuits ...
s, pen registers had obvious applications as diagnostic instruments for recording sequences of telephone dial pulses. In the United States, the clockwork-powered Bunnell pen register remained in use into the 1960s.
After the introduction of
tone dialing, any instrument that could be used to record the numbers dialed from a telephone came to be defined as a pen register. Title 18 of the
United States Code
The United States Code (formally The Code of Laws of the United States of America) is the official Codification (law), codification of the general and permanent Law of the United States#Federal law, federal statutes of the United States. It ...
defines a pen register as:
a device or process which records or decodes dialing, routing, addressing, or signaling information transmitted by an instrument or facility from which a wire or electronic communication is transmitted, provided, however, that such information shall not include the contents of any communication, but such term does not include any device or process used by a provider or customer of a wire or electronic communication service for billing, or recording as an incident to billing, for communications services provided by such provider or any device or process used by a provider or customer of a wire communication service for cost accounting or other like purposes in the ordinary course of its business
This is the current definition of a pen register, as amended by passage of the 2001
USA PATRIOT Act. The original statutory definition of a pen register was created in 1984 as part of the
Electronic Communications Privacy Act, which defined a "Pen Register" as:
A device which records or decodes electronic or other impulses which identify the numbers called or otherwise transmitted on the telephone line to which such device is dedicated.
A pen register is similar to a
trap and trace device. A trap and trace device would show what numbers had called a specific telephone, i.e., all ''incoming'' phone numbers. A pen register rather would show what numbers a phone had called, i.e. all ''outgoing'' phone numbers. The two terms are often used in concert, especially in the context of Internet communications. They are often jointly referred to as "Pen Register or Trap and Trace devices" to reflect the fact that the same program will probably do both functions in the modern era, and the distinction is not that important. The term "pen register" is often used to describe both pen registers and trap and trace devices.
Background
In ''
Katz v. United States'' (1967), the
United States Supreme Court
The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that turn on question ...
established its "
reasonable expectation of privacy" test. It overturned ''
Olmstead v. United States'' (1928) and held that warrantless
wiretaps were
unconstitutional
In constitutional law, constitutionality is said to be the condition of acting in accordance with an applicable constitution; "Webster On Line" the status of a law, a procedure, or an act's accordance with the laws or set forth in the applic ...
searches, because there was a reasonable expectation that the communication would be
private. From then on, the government was required to get a
warrant to execute a wiretap.
Twelve years later the Supreme Court held that a pen register is not a search because the "petitioner voluntarily conveyed numerical information to the telephone company." ''
Smith v. Maryland'', 442 U.S. 735, 744 (1979). Since the
defendant
In court proceedings, a defendant is a person or object who is the party either accused of committing a crime in criminal prosecution or against whom some type of civil relief is being sought in a civil case.
Terminology varies from one juris ...
had disclosed the dialed numbers to the telephone company so they could connect his call, he did not have a reasonable expectation of privacy in the numbers he dialed. The court did not distinguish between disclosing the numbers to a human operator or just the automatic equipment used by the telephone company.
The Smith decision left pen registers completely outside
constitutional protection. If there was to be any privacy protection, it would have to be enacted by Congress as statutory
privacy law.
Pen Register Act
The
Electronic Communications Privacy Act (ECPA) was passed in 1986 (Pub. L. No. 99-508, 100 Stat. 1848). There were three main provisions or Titles to the ECPA. Title III created the Pen Register Act, which included restrictions on private and law enforcement uses of pen registers. Private parties were generally restricted from using them unless they met one of the exceptions, which included an exception for the business providing the communication if it needed to do so to ensure the proper functioning of its business.
For
law enforcement agencies
A law enforcement agency (LEA) is any government agency responsible for law enforcement within a specific jurisdiction through the employment and deployment of law enforcement officers and their resources. The most common type of law enforcement ...
to get a pen register approved for
surveillance
Surveillance is the monitoring of behavior, many activities, or information for the purpose of information gathering, influencing, managing, or directing. This can include observation from a distance by means of electronic equipment, such as ...
, they must get a
court order
A court order is an official proclamation by a judge (or panel of judges) that defines the legal relationships between the parties to a hearing, a trial, an appeal or other court proceedings. Such ruling requires or authorizes the carrying o ...
from a judge. According to 18 U.S.C. § 3123(a)(1), the "court shall enter an
ex parte order authorizing the installation and use of a pen register or trap and trace device anywhere within the United States, if the court finds that the attorney for the Government has certified to the court that the information likely to be obtained by such installation and use is relevant to an ongoing criminal investigation". Thus, a government attorney only needs to certify that information will "likely" be obtained in relation to an 'ongoing
criminal investigation
Criminal investigation is an applied science that involves the study of facts that are then used to inform criminal trials. A complete criminal investigation can include Search and seizure, searching, interviews, interrogations, Evidence (law), ...
'. This is the lowest requirement for receiving a court order under any of the ECPA's three titles. This is because in ''
Smith v. Maryland'', the Supreme Court ruled that use of a pen register does not constitute a
search
Searching may refer to:
Music
* "Searchin', Searchin", a 1957 song originally performed by The Coasters
* Searching (China Black song), "Searching" (China Black song), a 1991 song by China Black
* Searchin' (CeCe Peniston song), "Searchin" (C ...
. The ruling held that only the content of a conversation should receive full constitutional protection under the
right to privacy
The right to privacy is an element of various legal traditions that intends to restrain governmental and private actions that threaten the privacy of individuals. Over 185 national constitutions mention the right to privacy.
Since the globa ...
; since pen registers do not intercept conversation, they do not pose as much threat to this right.
Some have argued that the government should be required to present "specific and articulable facts" showing that the information to be gathered is relevant and material to an ongoing investigation. This is the standard used by Title II of the ECPA with regard to the contents of stored communications. Others, such as
Daniel J. Solove,
Petricia Bellia, and
Dierdre Mulligan, believe that
probable cause
In United States criminal law, probable cause is the legal standard by which police authorities have reason to obtain a warrant for the arrest of a suspected criminal and for a court's issuing of a search warrant. One definition of the standar ...
and a warrant should be necessary.
Paul Ohm argues that
standard of proof
In a legal dispute, one party has the burden of proof to show that they are correct, while the other party has no such burden and is presumed to be correct. The burden of proof requires a party to produce evidence to establish the truth of facts ...
should be replaced/reworked for electronic communications altogether.
The Pen Register Act did not include an
exclusionary rule. While there were
civil remedies for violations of the Act, evidence gained in violation of the Act can still be used against a defendant in court. There have also been calls for Congress to add an
exclusionary rule to the Pen Register Act, as this would make it more analogous to traditional
Fourth Amendment protections. The penalty for violating the Pen Register Act is a misdemeanor, and it carries a prison sentence of not more than one year.
USA PATRIOT Act
Section 216 of the 2001
USA PATRIOT Act expanded the definition of a pen register to include devices or programs that provide an analogous function with Internet communications. Prior to the Patriot Act, it was unclear whether or not the definition of a pen register, which included very specific telephone terminology,
could apply to Internet communications. Most courts and law enforcement personnel operated under the assumption that it did, however, the
Clinton administration had begun to work on legislation to make that clear, and one
magistrate
The term magistrate is used in a variety of systems of governments and laws to refer to a civilian officer who administers the law. In ancient Rome, a '' magistratus'' was one of the highest ranking government officers, and possessed both judi ...
judge in
California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
did rule that the language was too telephone-specific to apply to
Internet surveillance.
The Pen Register Statute is a privacy act. As there is no constitutional protection for information divulged to a third party under the Supreme Court's expectation of privacy test, and the routing information for phone and Internet communications are divulged to the company providing the communication, the absence or inapplicability of the statute would leave the routing information for those communications completely unprotected from government surveillance.
The government also has an interest in making sure the Pen Register Act exists and applies to Internet communications. Without the Act, they cannot compel service providers to give them records or do Internet surveillance with their own equipment or
software
Software consists of computer programs that instruct the Execution (computing), execution of a computer. Software also includes design documents and specifications.
The history of software is closely tied to the development of digital comput ...
, and the law enforcement agency, which may not have very good
technological
Technology is the application of conceptual knowledge to achieve practical goals, especially in a reproducible way. The word ''technology'' can also mean the products resulting from such efforts, including both tangible tools such as ute ...
capabilities, will have to do the surveillance itself at its own cost.
Rather than creating new laws regarding Internet surveillance, the Patriot Act simply expanded the definition of a pen register to include computer software programs doing Internet surveillance by accessing information. While not completely compatible with the technical definition of a pen register device, this was the interpretation that had been used by almost all courts and law enforcement agencies prior to the change.
NSA call database controversy
When, in 2006, the Bush administration came under fire for having secretly collected billions of phone call details from regular Americans, ostensibly to check for calls to terror suspects, the Pen Register Act was cited, along with the
Stored Communications Act, as an example of how such domestic spying violated Federal law.
In 2013, the Obama administration sought a court order "requiring Verizon on an 'ongoing, daily basis' to give the NSA information on all telephone calls in its systems, both within the US and between the US and other countries". The order was approved on April 25, 2013, by federal Judge
Roger Vinson, member of the secret
Foreign Intelligence Surveillance Court (FISC), which court had been created by the
Foreign Intelligence Surveillance Act
The Foreign Intelligence Surveillance Act of 1978 (FISA, , ) is a Law of the United States, United States federal law that establishes procedures for the surveillance and collection of foreign intelligence on domestic soil.[Barack Obama
Barack Hussein Obama II (born August 4, 1961) is an American politician who was the 44th president of the United States from 2009 to 2017. A member of the Democratic Party, he was the first African American president in American history. O ...]
.
According to ''
The Guardian
''The Guardian'' is a British daily newspaper. It was founded in Manchester in 1821 as ''The Manchester Guardian'' and changed its name in 1959, followed by a move to London. Along with its sister paper, ''The Guardian Weekly'', ''The Guardi ...
'', "it is not known whether Verizon is the only cell-phone provider to be targeted with such an order, although previous reporting has suggested the NSA has collected cell records from all major mobile networks. It is also unclear from the leaked document whether the three-month order was a one-off or the latest in a series of similar orders".
Hemisphere DEA call database controversy
On September 1, 2013, the
DEA's Hemisphere Project was revealed to the public by ''
The New York Times
''The New York Times'' (''NYT'') is an American daily newspaper based in New York City. ''The New York Times'' covers domestic, national, and international news, and publishes opinion pieces, investigative reports, and reviews. As one of ...
''. In a series of
PowerPoint slides acquired through a lawsuit,
AT&T
AT&T Inc., an abbreviation for its predecessor's former name, the American Telephone and Telegraph Company, is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the w ...
is revealed to be operating a call database going back to 1987 which the DEA has warrantless access to with no judicial oversight under "administrative subpoenas" originated by the DEA. The DEA pays AT&T to maintain employees throughout the country devoted to investigating call records through this database for the DEA. The database grows by 4 billion records per day, and presumably covers all traffic that crosses AT&T's network. Internal directives instructed participants never to reveal the project publicly, despite the fact that the project was portrayed as a "routine" part of DEA investigations; several investigations unrelated to drugs have been mentioned as using the data. When questioned on their participation,
Verizon
Verizon Communications Inc. ( ), is an American telecommunications company headquartered in New York City. It is the world's second-largest telecommunications company by revenue and its mobile network is the largest wireless carrier in the ...
,
Sprint, and
T-Mobile T-Mobile is the brand of telecommunications by Deutsche Telekom
Deutsche Telekom AG (, ; often just Telekom, DTAG or DT; stylised as ·T·) is a partially state-owned German telecommunications company headquartered in Bonn and the largest telec ...
refused to comment on whether they were part of the project, generating fears that ''pen registers'' and ''trap and trace'' devices are effectively irrelevant in the face of ubiquitous private-public-partnership surveillance with indefinite data retention.
Information collected
Information that is legally collectible according to 2014 pen trap laws includes:
Phone
* Dialed numbers
* Received call numbers
* The time the call was made
* Whether the call was answered, or went to voice-mail
* The length of each call
* Content of SMS text messages
* Post-cut-through dialed digits--(digits dialed after call is connected, like banking
personal identification number
A personal identification number (PIN; sometimes RAS syndrome, redundantly a PIN code or PIN number) is a numeric (sometimes alpha-numeric) passcode used in the process of authenticating a user accessing a system.
The PIN has been the key to faci ...
(PIN) or prescription refill numbers)
* The real-time location of a cell phone to within a few meters
Email
* All email header information other than the subject line
* The email addresses of the people to whom an email was sent
* The email addresses of people who received the email
* The time each email is sent or received
* The size of each email that is sent or received
Internet
*
IP address
An Internet Protocol address (IP address) is a numerical label such as that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface i ...
, port, and protocol used
* The IP address of other computers on the Internet that information was exchanged with
* Time-stamp and size information of Internet access
* Protocol traffic analysis to obtain URL web addresses surfed on the web, emails posted or read, instant messages exchanged, and information posted onto message boards
See also
*
Call detail record
* ''
Smith v. Maryland''
* ''
United States v. Davis'', dealing with cell phone location data
References
Further reading
*
* {{cite journal , last=Kerr , first=Orin , authorlink=Orin Kerr , title=Internet Surveillance Law After the USA Patriot Act: The Big Brother That Isn't , journal=
Nw. U. L. Rev. , volume=97 , year=2003 , issue=2 , pages=607–673 , ssrn=317501
Law enforcement equipment
Surveillance
Privacy of telecommunications