IMEI (International Mobile Equipment Identity) is a 15-17-digit code that is given to every mobile phone. This number is used by service providers to uniquely identify valid devices. Specifically, IMEI code can enable a Global System for Mobile communication (GSM) or Universal Mobile Telecommunications Service (UMTS) network to prevent a misplaced or stolen phone from initiating calls. IMEI is also a part of mobile device management.
Uses of IME
Individuals who buy used phones can look up the IMEI number to check and see the phone is valid. Checking the number can also inform users on the country and network from which a device originated, the warranty, carrier information, and more similar details. Both law enforcement and intelligence services could also use an IMEI number in order to track devices within the accuracy of a few meters. The service provider can use the IMEI number to create a blacklist of stolen devices. If a user reports a phone as stolen, the service provider can add the number to the blacklist and block the phone from their network. The United Kingdom has a voluntary charter that is operated by mobile networks that helps ensure that any operator's blacklisting of a handset is communicated to the CEIR (Central Equipment Identity Register), then to all other networks within 48 hours.
How IME works
In most mobile communications devices, the IMEI appears on the display when the user enters the character sequence *#06# (star-pound-zero-six-pound) into the keypad. The IMEI code may also be printed inside the battery compartment. When a phone set is lost or stolen, the owner can call the CEIR (Central Equipment Identity Register) and blacklist the device according to its IMEI number. After that action, the set will, in most cases, become useless -- even if someone swaps out the unit's SIM card. However, although it is not an easy task, a skilled and determined cracker can sometimes change the IMEI number and use a stolen set to place calls.
Immediately after purchasing a mobile communications device, the owner should record the IMEI code in a secure place so that it can be quickly accessed in the event of loss or theft.