  In recent years, there has been an increasing interest in false base station
detection systems. Most of these rely on software that users download into
their mobile phones. The software either performs an analysis of radio
environment measurements taken by the mobile phone or reports these
measurements to a server on the Internet, which then analyzes the aggregated
measurements collected from many mobile phones. These systems suffer from two
main drawbacks. First, they require modification to the mobile phones in the
form of software and an active decision to participate from users. This
severely limits the number of obtained measurements. Second, they do not make
use of the information the mobile network has regarding network topology and
configuration. This results in less reliable predictions than could be made. We
present a network-based system for detecting false base stations that operate
on any 3GPP radio access technology, without requiring modifications to mobile
phones, and that allows taking full advantage of network topology and
configuration information available to an operator. The analysis is performed
by the mobile network based on measurement reports delivered by mobile phones
as part of normal operations to maintain the wireless link. We implemented and
validated the system in a lab experiment and a real operator trial. Our
approach was adopted by the 3GPP standardization organization.
