The 1500$ Cell phone Intercept System
The calls that are being intercepted, especially the encrypted ones, are included in the encryption algorithms, by providing the operator of the system call details and content that can be also recorded.
In this way, after the interception is completed, the voice calls are routed to their proper channels. Taking into account the fact that for creating this system were used simple materials and that it is very similar to the interception devices used by many intelligence agencies and law enforcement agencies, some will say that the system will be a successful one.
The actual interception systems, the currently IMSI catchers are working by sending in signals to the mobile phones, usually stronger than the average GSM towers. In this way, the devices are tricked to send the calls to these devices, which are later sent back to the GSM towers.11