IMSI catches has long been used by law enforcement personnel to track suspects and here is how it works.
The number is stored in the read-only section of a SIM card and with the mobile operator.
source: www.techworm.net
Cell phone users can be tracked easily using just WiFi and here’s how
WiFi can be turned into a IMSI catcher and using this approach, cell phone users can be tracked anywhere in the WiFi’s range
