Can the government or any other agency use cell phones as a microphone? Even if the phone is off or on?

Generally speaking, if the cell phone is truly off (no power applied), then it is useless as a surveillance device... unless it has been specially modified.

If it is "on," but not being used in an active phone call (in standby mode) then it can be used to track the phone's location in many service areas.

I am not aware of remote turn-on of microphones (as a normal feature) in any except GSM type cell phones. If this is a concern there are two solutions: Keep the phone turned off and/or remove the battery when not in use, or keep your phone into a special radio-frequency shielded pouch so it can't commumicate.

This is not to say cell phones have not been used as bugs. Modified spy phones are being sold on the Internet. The look like regular cell phones. They work like regular cell phones. But... they allow an eavesdropper to call the phone (silently) and listen into on-going calls and anyone speaking near the phone - even when it is not in use!

The Number One Cell Phone Eavesdropping Trick...
The eavesdropper hides the cell phone in the area to be monitored and takes advantage of the following normal cell phone features...

1. Activation of the "ringer mute" feature so that the phone does not make any noise when called.
2. Activation the "autoanswer" feature so that the phone turns on whenever called.
3. Power the phone using its AC charger so that it can remain ready to eavesdrop at all times.

The clever eavesdropper will use a pre-paid cell phone purchased with cash so that even if the phone is discovered, it can't be traced back to the eavesdropper.

On the bright side... a well equipped sweep service should find this type of eavesdropping device quite easily.


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