An International Mobile Subscriber Identity-catcher, or IMSI-catcher, is a telephone eavesdropping device used for intercepting mobile phone traffic and tracking movement of mobile phone users. Essentially a “fake” mobile tower acting between the target mobile phone and the service provider’s real towers, it is considered a man-in-the-middle (MITM) attack. IMSI-catchers are used in some countries by law enforcement and intelligence agencies, but their use has raised significant civil liberty and privacy concerns and is strictly regulated in some countries such as under the German Strafprozessordnung (German) (StPO / Code of Criminal Procedure). Some countries do not even have encrypted phone data traffic (or very weak encryption), thus rendering an IMSI-catcher unnecessary.
Every mobile phone has the requirement to optimize the reception. If there is more than one base station of the subscribed network operator accessible, it will always choose the one with the strongest signal. An IMSI-catcher masquerades as a base station and causes every mobile phone of the simulated network operator within a defined radius to log in. With the help of a special identity request, it is able to force the transmission of the IMSI.
ANTRAX solution has effective features to make your gateway become invisible for IMSI catcher.
Read more about GSM termination security here