Cellular Phone Security

I recently lost my cellphone and that was when I came to know about IMEI number and why the Government of India is not allowing China made cellphones without IMEI number to work in India. My cellphone was a cheap Nokia one and losing it gave me endless joy as it helped me get a newer better version. But what if you have a high end phone and you lose it. There is a way to ensure that if you do not get your cellphone back, you can at least ensure that whosoever gets it is not able to use it too. Read On.

What to do if your cellphone is stolen?

Every phone has a IMEI number. IMEI - International Mobile Equipment Identity or IMEI number is a unique which helps identify mobile and some satellite phones. IMEI number is usually found in the battery compartment of the mobile phone and should not be confused with the IMSI number about which we will learn more later. The primary use of the IMEI number is to provide more security by uniquely identifying every phone working on the network. We can easily know the IMEI number of our phones by pressing *#06# into the keypad.

So how can IMEI number prevent our cellphone from getting stolen?

The IMEI number is mapped to the device and this mapping has a one to one relationship. This means that there is one IMEI number for every single device. The moment we start using a cellular phone with a valid IMEI number, the same is transmitted to and stored by the service provider in a register called as the EIR - Equipment Identity Register. GSM network operators maintain three lists of international mobile equipment identities (IMEI) in their Equipment Identity Register (EIR):

# grey - GSM mobile phones to be tracked

# black - Barred GSM mobile phones

# white - Valid GSM mobile phones

Hence if the user tries to connect to the network and get on call using the Barred GSM mobile phone, he/she will be barred from using the network.

But what if the phone is taken to another region where our network provider and hence his EIR are both not accessible. That is when CEIR comes in to play.

CEIR - Central Equipment Identity Register is a database of IMEI number of blacklisted devices. Chinese mobiles have been banned in India if they do not possess IMEI number and the same has been facilitated by the use of EIR and CEIR.

Network Operators Benefit through IMEI number?

The increasing number of high end phones in the market also increases vulnerability of network operators due to spamming, spoofing and hacking. Spoofing can change the identity of the user and this might lead to revenue leakage. Network operators benefit from having a built in mechanism that can help them keep suspicious cellular phones in check.

Mobile Phone Tracking through IMEI number

Cellular phones can be tracked and their location can be established using Mobile Phone Tracking mechanisms. Mobile Phones can be tracked by cellular towers, software in the cellular phones or by using a combination of both these mechanisms.

Cellular towers can track a phone in its cell or other cells by interpreting signals and signal strength from the cellular phone and also by using methods such as triangulation.

Handset based techniques can be implemented when the mobile device is equipped with GPS or a software that helps track its location.

Sometimes methods that utilize both of these techniques are also used to track the cellular phone. If you are buying a high end smart phone then you can be rest assured that it will be having most of the security mechanisms already built into its system.

IMEI number vs IMSI

The IMEI number is associated with the device and has no relation whatsoever to the subscriber. The IMEI number should not be confused with the IMSI - International Mobile Subscriber Identity which is used to create relevant entries about the phone in the HLR - Home location register or the VLR - Visitors Location Register. The IMSI is stored in the SIM card. It is a 15 (or sometimes 14)digit long number which consists of the Mobile Country Code (MCC) which is 3 digits long, and is followed by the Mobile Network Code (MNC), either 2 digits (European standard) or 3 digits (North American standard). The remaining digits are the mobile station identification number (MSIN) within the network's customer base. The IMSI is used to activate/deactivate the customer account by the telecom service provider when the customer lodges such a request. So when we call the call center and ask the service provider to stop billing on our card, this is the number that they use to deactivate the customer account.