The FBI appears to have begun using a novel form of electronic surveillance in criminal investigations: remotely activating a mobile phone's microphone and using it to eavesdrop on nearby conversations. [...]

The U.S. Commerce Department's security office warns that "a cellular telephone can be turned into a microphone and transmitter for the purpose of listening to conversations in the vicinity of the phone." An article in the Financial Times last year said mobile providers can "remotely install a piece of software on to any handset, without the owner's knowledge, which will activate the microphone even when its owner is not making a call."

Nextel and Samsung handsets and the Motorola Razr are especially vulnerable to software downloads that activate their microphones, said James Atkinson, a counter-surveillance consultant who has worked closely with government agencies. "They can be remotely accessed and made to transmit room audio all the time," he said. "You can do that without having physical access to the phone." [...]

Other mobile providers were reluctant to talk about this kind of surveillance. Verizon Wireless said only that it "works closely with law enforcement and public safety officials. When presented with legally authorized orders, we assist law enforcement in every way possible."

This is a good hack; I wonder what the mechanism is. Do these phones do automatic software updates? Or would it be necessary to trick the user into downloading a trojan?