On 2/15/07, Eugen Leitl
... In an effort to explain this issue in a more demonstrative and somewhat less technical manner, I'm pleased to announce a short free video (under six minutes): "Is Your Cell Phone Bugged?"
good stuff. predominantly the following are the best give away, and seem to apply to some models and not others: [via http://lauren.vortex.com/archive/000202.html] "A well designed bug program could try to minimize the obviousness of this by quickly dropping the bug call if the phone owner tried to make an outgoing call, or drop the bug connection if an incoming call tried to ring through. But if the bug is up and running, that's the only transmission path that is available on the phone at that time for the vast majority of currently deployed cell phones." this is undetectable on some models, and causes a few seconds of "one way conference" style problems on others. basically, you answer/call, and get silence, neither party can hear each other for a few seconds. - "But if your battery seems to be running out of juice far too early (despite what the phone's battery status display might claim), that might be an indication that your phone is being used to transmit behind your back (though a worn out battery or inaccurate battery status display could also be the culprits). Another clue that a phone may have been transmitting without your permission is if it seems unexpectedly warm. You've probably noticed how most cell phones heat up, especially on longer calls. This is normal, but if you haven't been on any calls for a while and your cell phone is warm as if long calls were in progress, you have another red flag indication of something odd perhaps going on." this is a good indicator, and particularly on some phones with excellent battery life (some sanyo/motorola models) it becomes real obvious when unusual battery drain is occurring. - "Finally, if you use a GSM phone (like the vast majority of phones around the world, including Cingular and T-Mobile in the U.S.) you have a virtually foolproof way to know if you phone is secretly transmitting in voice mode. You've probably noticed the "buzzing" interference that these phones tend to make in nearby speakers when calls or data transmissions are in progress. A certain amount of periodic routine communications between cell phones and the networks will occur while the phones are powered on -- even when calls are not in progress -- so short bursts of buzzing between calls (and when turning the phones on or off) are normal. But if you're not on a call, and you hear a continuing rapid buzz-buzz-buzz in nearby speakers that lasts more than a few seconds and gets louder as you approach with your phone, well, the odds are that your phone is busily transmitting, and bugging is a definite possibility. Note that this particular test is much less reliable with non-GSM phones that use CDMA (e.g. Sprint/Verizon phones), since CDMA's technology is less prone to producing easily audible local interference. This strongly suggests that CDMA phones may be preferred for such bugging operations." this is a smoking gun on a GSM phone, and unfortunately it does not work against CDMA, as mentioned. take the battery out, it works great. :)