ESD's Cryptophone 500 spotted 17 of the fake cellular towers on casual drives around the USA, including one at the South Point Casino in Las Vegas. The baseband processor, which controls the phone's radio, is notoriously insecure and vulnerable to over-the-air attacks; it can serve as a back-door to your phone's main OS. The fake "interceptor" towers force your phone to back \\down to an easy-to-break 2G connection, then goes to work:
Read about it here...
http://boingboing.net/2014/09/01/fake-phone-attacking-cell-tow.html