In many regions of the world, a mobile communications terminal such as a cell phone is not locked to a specific network service provider. Instead, subscribers to a network are issued a smart card, such as a Subscriber Identity Module (SIM) or other removable plastic card that uniquely identifies the user account to the network, handles authentication and provides data storage for user data such as phone numbers and network information. The SIM may also contain applications that can be accessed by the phone. The phone itself is fungible because a subscriber can use any phone that accepts a SIM.
SIM cards often operate in conjunction with a phone that operates in a wireless network environment such as the Global System for Mobile Communications (GSM) network. In a GSM environment, any phone can be used by inserting a SIM card into the phone and accessing the network. More significantly, however, inserting a SIM card into a GSM phone not only provides access to the network, but also provides access to any private content stored in the internal memory of the phone. If an owner loses, loans, discards, or otherwise loses control of the phone, anyone with a SIM card can access the owner's private content on the phone.