If you weren't paranoid enough already about people spying on you, this article should put you over the top. Two researchers say they have found a way to exploit weaknesses in the mobile telecom system to legally spy on people by figuring out the private cell phone number of anyone they want, tracking their whereabouts, and listening to their voice mail.

The first part of the operation involves getting a target's cell phone number from a public database that links names to numbers for caller ID purposes. DePetrillo used open-source PBX software to spoof the outgoing caller ID and then automated phone calls to himself, triggering the system to force a name lookup.

Next up is matching the phone number with a geographic location. The SS7 (Signaling System) public switched network routes calls around the world and uses what's called the Home Location Register to log the whereabouts of numbers so networks can hand calls off to one another, DePetrillo said. Individual phones are registered to mobile switching centers within specific geographic regions and they are logged in to that main register, he said.

Only telecom providers are supposed to have access to the location register, but small telcos in the EU are offering online access to it for a fee, mostly to companies using it for marketing data and cost projections, according to DePetrillo.