Beware: Your GSM mobiles too can be cloned -The Times of India
What is cell phone cloning?
It is taking security data from a cell phone and reprogramming another with it. It works like an extension works with a land line. Though calls can be made from both phones, it’s the original that will be billed.

How is it done?
Every cell phone has a unique factory-set electronic serial number (ESN) and telephone number (MIN). To clone your phone, all someone needs to do is get these and reprogramme another phone with them.

How easy is it?
Very, if you have the software and equipment, all of which is freely available on the Internet.

The background
Cell phone cloning is very popular in countries with high immigrant population where calling home is expensive. Cloning can be for calls, mischief or criminal intent.