Covert listening device

A covert listening device, more commonly known as a bug or a wire, is usually a combination of a miniature radio transmitter with a microphone. The use of bugs, called bugging, is a common technique in surveillance, espionage and in police investigations.

A bug does not have to be a device specifically designed for the purpose of eavesdropping. For instance, with the right equipment, it is possible to remotely activate the microphone of cellular phones, even when a call is not being made, to listen to conversations in the vicinity of the phone.

Remotely activated mobile phone microphones
Mobile phone (cell phone) microphones can be activated remotely, without any need for physical access. This "roving bug" feature has been used by law enforcement agencies and intelligence services to listen in on nearby conversations. A United States court ruled in 1988 that a similar technique used by the FBI against reputed former Gulfport, Mississippi cocaine dealers after having obtained a court order was permissible.

Automobile computer systems
In 2003 the FBI obtained a court order to surreptitiously listen in on conversations in a car, through the car's built-in emergency and tracking security system. A panel of the 9th Circuit Court of Appeals prohibited the use of this technique because it involved deactivating the device's security features.

Examples of use

 * Embassies and other diplomatic posts are often the targets of bugging operations.
 * The Soviet embassy in Ottawa was bugged by the Canadian government and MI5 during its construction.
 * Extensive bugging of the West German embassy in Moscow by the KGB was discovered by German engineer Horst Schwirkmann, leading to an attack on Schwirkmann in 1964.
 * The Great Seal bug was hidden in a copy of the Great Seal of the United States, presented by the Soviet Union to the United States ambassador in Moscow in 1946 (not discovered until 1952). The bug was unusual in that it had no power source or transmitter, making it much harder to detect – it was a new type of device, called a passive resonant cavity bug. The cavity had a metallic diaphragm that moved in unison with sound waves from a conversation in the room.  When illuminated by a radio beam from a remote location, the cavity would return a frequency modulated signal.
 * The United States Embassy in Moscow was bugged during its construction in the 1970s by Soviet agents posing as laborers. When discovered in the early 1980s, it was found that even the concrete columns were so riddled with bugs that the building eventually had to be torn down and replaced with a new one, built with U.S. materials and labor. For a time, until the new building was completed, embassy workers had to communicate in conference rooms in writing, using children's "Mystic Writing Tablets".
 * In 1990, it was reported that the embassy of the People's Republic of China in Canberra, Australia, had been bugged by the Australian Secret Intelligence Service as part of the UKUSA Project Echelon.
 * Colin Thatcher, a Canadian politician, was secretly recorded making statements which would later be used to convict him of his wife's murder. The recording device was concealed on a person who Thatcher had previously approached for help in the crime.
 * Electronic bugging devices were found in March 2003 at offices used by French and German delegations at the European Union headquarters in Brussels. Devices were also discovered at offices used by other delegations. The discovery of the telephone tapping systems was first reported by Le Figaro newspaper, which blamed the US.
 * The car of Thomas Hentschell, who was involved in the Melbourne gangland killings, was bugged by police.
 * In 1999, the US expelled a Russian diplomat, accusing him of using a listening device in a top floor conference room used by diplomats in the United States Department of State headquarters.
 * In 2001, the government of the People's Republic of China announced that it had discovered twenty-seven bugs in a Boeing 767 purchased as an official aircraft for President Jiang Zemin.
 * In 2003, the Pakistani embassy building in London was found bugged; contractors hired by MI5 had planted bugs in the building in 2001.
 * In 2003, Alastair Campbell (who was Director of Communications and Strategy from 1997-2003 for the UK PM) in his memoirs The Blair Years: The Alastair Campbell Diaries alleged that two bugs were discovered in the hotel room meant for visiting British PM Tony Blair planted by Indian intelligence agencies.The alleged bug discovery was at a hotel during PM Tony Blair's official visit to New Delhi in 2001. Security services supposedly informed him that the bugs could not be removed without drilling the wall and therefore he changed to another room.
 * In 2004, a bug was found in a meeting room at the United Nations offices in Geneva.
 * In 2008 it was reported that an electric samovar presented to Elizabeth II in about 1968 by a Soviet aerobatic team was removed from Balmoral Castle as a security precaution amid fears that its wiring could contain a listening device.