Most mobile devices will connect to any base station that appears legitimate. That behaviour is what makes IMSI catchers possible. Mobile devices use International Mobile Subscriber Identifiers (IMSI) to authenticate and communicate across cellular networks. IMSI catchers exploit this by impersonating legitimate base stations, causing nearby phones to connect to them instead of the real network. In doing so, they collect SIM and device identifiers (such as IMSI or IMEI), along with signalling metadata that can be used to estimate presence and rough location. This does not require breaking applications or accessing encrypted content. It relies entirely on standard network behaviour. These techniques exploit trust within the network itself, sometimes forcing devices onto older or less secure protocols. Although heavily regulated and detectable, their effectiveness highlights how much signalling information mobile networks already expose by design.…