more on How To Tell If Your Cell Phone Is Bugged

Begin forwarded message:

From: Phil Karn <[email protected]>
Date: December 4, 2006 9:26:42 PM EST
To: [email protected]
Cc: [email protected]
Subject: Re: [IP] How To Tell If Your Cell Phone Is Bugged

> A story is making the rounds right now regarding FBI use of cell
> phones as remote bugs (e.g. http://news.com.com/ 
> 2100-1029-6140191.html ).

Personally I am much more concerned about the use of mobile phones as  
physical tracking devices than as audio bugs.

Every mobile phone, whenever it's turned on, is *already* a physical  
tracking device. *EVERY* mobile phone. Even when idle, phones  
periodically transmit "registration" messages to the base station so  
that the network will know where to deliver an SMS or inbound call  
message. (This is why airlines require phones to be completely shut  
off in flight; it's not sufficient to simply avoid making calls to  
prevent transmissions.)

In the old analog days, low user populations and lack of automatic  
wide-area roaming sometimes made it practical to "flood" paging  
messages over a network so that mobile registrations were not  
necessary. But flood paging has long become impractical in digital  
cellular networks.

Cellular networks have a perfectly legitimate need to know where you  
are, at least to the nearest cell sector, so they can do their job.  
The recent addition of GPS reporting to E911 calls increases the  
positioning accuracy still further.

And this is what's so problematical. Location data, like so much  
other personal data necessarily collected in the routine operation of  
modern communication networks, has both benign -- lifesaving, even --  
and harmful uses.

At least the content confidentiality problem has an effective  
technical defense (end to end encryption) even if it isn't widely  
used. But there seems to be no such technological defense against the  
abuse of cellular location data. Your only choice is to turn your  
phone off, preferably by removing the battery, when you don't want to  
be tracked. If you turn it on, even for a moment, the system will  
again know where you are.

Another alternative is to forego a cell phone in favor of a one-way  
pager, if they're even still available. But should you answer a page,  
even with a pay phone, you could in principle still be tracked unless  
you encode your pages.