How Wiretapping Works

When many people think of wiretapping, they imagine the CIA, FBI or state police listening in on criminals’ phone conversations in order to build criminal cases against them. While law enforcement agencies do tap into the conversations of criminals in order to disrupt and shut down criminal enterprises, many instances of wiretapping are undertaken by citizens against fellow citizens.

In fact, perhaps the most common form of wiretapping is plain old “listening in” to the conversations of loved ones. Maybe a parent wants to find out what a child is up to and listens in on a conversation between the child and a friend. Maybe a spouse wants to find out if her husband is cheating and listens in on his conversations with friends. Is that legal?

Wiretapping occurs all the time in espionage and crime movies. Spies and gangsters know the enemy is listening, so they speak in code over the phone and keep an eye out for bugs. In the real world, we may not think much about wiretapping.

History of wiretapping

Wiretapping laws have always had difficulty in balancing privacy rights of individuals with the concerns of state and law enforcement. While wiretapping has existed since the days of the telegraph, the first recorded wiretapping by law enforcement was in the 1890s in New York City. In the 1910s, the New York State Department found that police had wiretapped entire hotels without warrant.

The department claimed it did not violate Fourth Amendment rights, on the grounds that the amendment only covers tangible communications, such as mail, and that it only breached those rights where placing of taps involved trespassing. (That restriction was no block to enforcement, as officials could tap a telephone company’s switching station.)

The exemption of intangibles from the fourth amendment was upheld with the conviction of Roy Olmstead — a former prohibition police officer turned multimillionaire bootlegger — in 1925. However, the case had gone to the ninth circuit court of appeals.

In 2008, Wired and other media reported a lamplighter disclosed a “Quantico Circuit”, a 45-megabit/second DS-3 line linking a carrier’s most sensitive network in an affidavit that was the basis for a lawsuit against Verizon Wireless. The circuit provides direct access to all content and all information concerning the origin and termination of telephone calls placed on the Verizon Wireless network as well as the actual content of calls, according to the filing.

The most recent case of U.S. wiretapping was the NSA warrantless surveillance controversy discovered in December 2005. It aroused much controversy after then-President George W. Bush admitted to violating a specific federal statute (FISA) and the warrant requirement of the Fourth Amendment to the United States Constitution. The President claimed his authorization was consistent with other federal statutes (AUMF) and other provisions of the Constitution, it was necessary to keep America safe from terrorism and could lead to the capture of notorious terrorists responsible for the September 11 attacks in 2001.

One difference between foreign wiretapping and domestic wiretapping is that, when operating in other countries, “American intelligence services could not place wiretaps on phone lines as easily as they could in the U.S.” Also, domestically, wiretapping is regarded as an extreme investigative technique, whereas outside of the country, the interception of communications is huge. The National Security Agency (NSA) “spends billions of dollars every year intercepting foreign communications from ground bases, ships, airplanes, and satellites”.

FISA distinguishes between U.S. persons and foreigners, between communications inside and outside the U.S., and between wired and wireless communications. Wired communications within the United States are protected since intercepting them requires a warrant.

Modern-day wiretapping

The argument that new technologies are not covered by the law is often used to justify increased monitoring of private citizens. The Electronic Communications Privacy Act (ECPA), despite its name, loosened the requirements for non-voice based communications, and the Communications Assistance for Law Enforcement Act (CALEA) of 1994 allowed law enforcement to fine telcos $10,000 a day if the company’s networks are not built with wiretapping capabilities.


The number of state wiretaps reported in which encryption was encountered increased from 7 in 2015 to 57 in 2016. In 48 of these wiretaps, officials were unable to decipher the plain text of the messages. A total of 68 federal wiretaps were reported as being encrypted in 2016, of which 53 could not be decrypted. Encryption was also reported for 20 federal and 19 state wiretaps that were conducted during a previous year, but reported to the AO for the first time in 2016. Officials were not able to decipher the plain text of the communications in any of the state intercepts or in 13 of the federal of intercepts.


We’ve seen that tapping a wire is something like plugging an appliance into the electrical circuit running through your house. When you plug an appliance into the wall, the appliance draws power from the electrical current flowing in this circuit. The current in a phone line provides power as well, but it also carries information — a pattern of current fluctuations that represents the air-pressure fluctuations of sound waves. A wiretap is a device that can interpret these patterns as sound.

One simple sort of wiretap is an ordinary telephone. In a way, you are tapping your own phone line whenever you hook up another phone in your house. This isn’t considered wiretapping, of course, since there’s nothing secretive about it.

Wiretappers do the same basic thing, but they try to hide the tap from the person they’re spying on. The easiest way to do this is to attach the phone somewhere along the part of the line that runs outside the house. To configure a phone for tapping, the wiretapper just cuts one of the modular plugs (the part you insert in the jack) off a piece of phone cord so that the red and green wires are exposed. Then, the tapper plugs the other end of the wire into the phone and attaches the exposed wires to an accessible, exposed point on the outside phone line.

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