Sunday, April 12, 2009

Blacklisted Phones

What is it all about?

A phone may be blacklisted (or barred) for many different reasons, but the most common reason is that it has been reported either lost or stolen! Mobile Service Providers in Pakistan have the facility to blacklist a handset.

If you are unfortunate enough to either lose or even worse have your phone stolen you should report it to your service provider (your network) immediately! Your service provider can then blacklist the handset so that it can no longer be used to make or receive any calls. The networks do this by adding your phones serial number onto a national blacklist database (CPLC). Effectively the handset becomes absolutely useless and the thief is in possession of a pretty paper weight!

So How does blacklisting Work?

Every mobile phone has a unique serial number. This serial number is called the IMEI number (International Mobile Equipment Identity). It can normally be found underneath the phones battery and it is 15 digits long.

Now each time you switch your phone on or attempt to make a call the network systems check the IMEI number of the handset you are using. At this point the IMEI number of your handset is cross referenced with the CPLC. If the IMEI number of your handset is on the CPLC then the network will either:

1) Refuse to send a signal to your phone (No signal strength at all)

2) Or will supply a signal but will not allow any outgoing or incoming calls.

If your IMEI number is on the CPLC your handset is blacklisted and therefore useless. By spreading the word that “stolen handsets will not work” it is hoped that street crime can be reduced!

How to check if your phone is blacklisted?

If you place an active SIM into a blacklisted handset you phone will not show any signal strength at all! If the handset is a Nokia then a “SIM card registration failed” message will also be displayed. If your handset is an Ericsson then an “Invalid Mobile” message will be displayed. For most other manufacturers the handset will simply show no signal!

How Do Criminals Get Around The Blacklisting Scheme?

So now that handsets are blacklisted on all networks what do the criminals do to get around this? They find ways to change handset IMEI numbers! Never the less it is possible to change IMEI numbers on certain handsets. So if an individual obtains a blacklisted handset, they can change the IMEI number and the handset will then work again!!

In my opinion the responsibility now lies with the handset manufactures. They need to make it as difficult as possible to change IMEI numbers. To be fair some manufactures are doing their bit (but some are not!). For example Nokia’s older DCT 3 range of handsets have been well and truly cracked. Anyone that searches the Internet for a short period of time would be able to find an IMEI change solution. BUT Nokia’s new DCT4 range of handsets remains un beaten with regards to changing the IMEI. This is largely down to the type of memory used to store the IMEI number. Nokia have chosen to use OTP (one time programmable) memory, which by its very name indicates that data cant be over written. (unless you change the UEM/memory chip - technically this is out of the realms of most criminals!)

The criminals do have an alternative to changing IMEI’s, and this is to send the barred handsets overseas! A mobile phone that is blacklisted in some other country may work in Pakistan and vice versa.

The solution to this exporting problem is simple. Rather than a national database the mobile industry is now looking to build an international database. If/when this is introduced blacklisted handsets will not work anywhere in the world! (The international database idea sounds good! But it does have obstacles to overcome, as many African networks claim that it would be too expensive to upgrade their equipment to support such a system)

A little time on Google and i found many IMEI changers free of cost, though i never tried any because i didn’t have any cable or an old phone to play with. I have a few friends who work in Saddar Mobile Market, when i inquired them about blacklisted phones, i was amazed , they already knew about such stuff and are themselves repairing blacklisted phones. For a Nokia N95, they were charging Rs. 1500. I’m still searching the internet, may be i might find something that may help us recognize such phones.

How To Block Your Stolen Phone?

To block your mobile phone call at 021-5682222, 6583334 to CPLC (Citizen Police Liaison Committee) or to 15, you can also call directly to PTA at the following number 0800-25625. They will get some basic info and the IMEI number of your lost mobile set. They will register IMEI (International Mobile Equipment Identity) of your cell phone and will request all the mobile operators to block this IMEI on their networks. You can also fax your complaint to CPLC at 021-5683336 or can send an email to PTA at or visit the site which is

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