Every GSM mobile phone has a unique serial number, called an International Mobile Equipment Identity (IMEI) number. This number is built into the phone’s hardware by the manufacturer, not the SIM card which is supplied by the mobile carrier and can be removed and inserted into another phone. In the case of a theft, an IMEI number can be used to disable a phone so that it can no longer be used on any network. Every (reputable) mobile phone operator subscribes to the IMEI Database, a worldwide blacklist of IMEI numbers that have been reported stolen. Subscribers will not activate a phone with an IMEI number in the blacklist database, preventing thieves from simply taking your phone to another company after your operator disables it on their network.

You don’t need to know your IMEI number to report a stolen phone – a phone call to your mobile phone operator will suspend your account. Most thieves steal phones to steal the service, placing international calls and running up data charges until the phone is deactivated, at which point they will ditch it. However, if you have an expensive phone the thief may try to sell it and/or reactivate it, in which case reporting the IMEI number will prevent the phone from being activated by another company or in another country.

Finding Your IMEI Number
For obvious reasons, it’s far less convenient to discover your phone’s serial number after it’s already been stolen, so make a habit of writing down the serial numbers of all your new devices as soon as you purchase them and store them in a safe place. Finding an IMEI number on a phone that is turned on is quite simple: dial *#06# on almost any model phone and the 15-digit IMEI number will be displayed on the screen. Most phones’ operating systems should also include an information screen that will tell you the IMEI number if you forget this code (on the iPhone, for example, you can find the IMEI number under Settings>General>About).

If you don’t want to or can’t turn on the phone, the IMEI number is also usually printed inside the battery compartment of mobile phones. Pop the case off your phone (assuming it has a removable case), remove the battery and look for the IMEI number.

Finally, the box your mobile phone came in should have the IMEI number printed on it. Hanging on to the box is a great way to keep a record of your serial numbers in case your phone is ever stolen.

If you do find yourself in a situation where your phone has been stolen and you don’t know its IMEI number, you can either look for the phone’s original box or simply call your mobile phone operator to disable your account.

Reporting a Stolen Phone
The effectiveness of the IMEI system means that thieves know they have to act fast, which unfortunately means that you also have to act fast once you discover your phone has been stolen. Mobile phone thieves operate in a similar manner as credit card thieves, trying to rack up as many charges as they can before the account is canceled.

Call your mobile phone operator as soon as possible and tell them you need your account to be suspended because your phone has been stolen. Once this has been accomplished your account will not incur any charges from the thief’s activities (most operators will also waive any charges the thieves may have already made; carefully review your account activity with your operator and let them know the last legitimate activity you performed before the phone was stolen). If you know your IMEI number, give it to your operator and specifically ask them to add the phone to the IMEI Database blacklist. This will prevent the thief from enjoying their ill-gotten gains on another mobile network. Depending on your operator, they may also ask you for a police report.

Limitations
The IMEI is not a full-proof system; a phone’s serial number can be faked, although this requires fairly sophisticated knowledge and equipment. Someone may clone your IMEI number and trick your operator into charging your account for their usage, or your stolen phone may be given a new IMEI number which allows the thief to activate it. However the IMEI system’s robustness and universal adoption in the industry means that it works for the vast majority of cases, provided you remember to record your IMEI number ahead of time and react quickly if your phone is stolen.

Future Outlook
Smartphones are already beginning to incorporate features allowing lost phones to be located by GPS, or even remotely erased to protect sensitive data in the event of a theft. As these features spread, expect law enforcement agencies to start gaining access to these systems, allowing them to track the location of stolen phones the way LoJack allows police to track stolen cars, maybe even remote access to the phone’s camera or voice log to try and identify the perpetrator. The ultimate goal of the next generation of IMEI may not be to simply disable your stolen phone, but to actually get it back for you.