Bug with transmitter

Most bugs use a radio transmitter, but there are many other options for carrying a signal: radio frequencies may be sent through the main wiring of a building and picked up outside; transmissions from a cordless phone can be monitored; and it is possible to pick up the data from poorly configured wireless computer networks or tune in to the radio emissions of a computer monitor or keyboard.

Bugs come in all shapes and sizes. The original purpose of bugs was to relay sound, but today the miniaturization of electronics has progressed so far that even commercially-available bugs designed to carry TV signals are usually the size of a cigarette packet. Professional bugs can fit into pens, calculators and other commonplace items. Some are only the size of small shirt buttons, although the power and operational life of the smallest bugs is very short.

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.

Remotely activated mobile phone microphones

Some mobile phone (cell phone) microphones can be activated remotely, without any need for physical access, even when the phone is switched off. This roving bug feature is reportedly being used by law enforcement agencies and intelligence services to listen in on nearby conversations. A United States court ruled in 1986 that a similar technique, used by the FBI against reputed former Gulfport Mississippi mobster type cocaine dealers "Bennett Branch" and "Don Tomlinson" dealing cocaine directly under the authority of mob boss David "The Eagle" Easterling after having obtained a court order, was permissible. While it is not possible to do this with every mobile phone as of 2006, some models are susceptible to being remotely reprogrammed (over the air using methods meant for delivering upgrades (Firmware updates and maintenance) with this capability without the knowledge of its owner. Examples for such mobile phones are Motorola Razr and Samsung 900 series mobile phones.

Realization

For the mobile phone as eavesdropping tool the OTA update function is not used to transfer firmware or other official software but rather "special" software which can offer one of the following features:

• The standard software user interface is manipulated or overwritten in a way that phone calls which are done over the infiltrated program are not shown.
• This special software is able to accept an incoming connection (e.g. a call from a certain number) without showing this on the mobile phones user interface. This is possible as long as no connection is existing at the same time.
• If the phone gets switched off the software only pretends this (e.g. turning off the display). Incoming or outgoing connections are still possible.
• Even though the mobile phone gets switched off it is in a standby comparable status. The "special" software is operating in the background like the alarm clock function. Connection establishment or answering a call in this status is already possible.