SIM (subscriber identification module) – Technology used to identify the user for mobile subscription service, like your cell phone carrier. SIM card is a tiny card used in mobile phones to store this user information. It can be easily removed and inserted into a different device without any memory/data loss. SIM card stores such info as your phone book, SMS messages, your phone number, etc…
As mentioned SIM cards are used by cell phone carriers that work on GSM network. GSM allows users to track and perform surveillance on other network users.
