So, what is the modus operandi of a typical fraudster?

Every mobile handset has a unique factory-coded Electronic Serial Number (ESN) and a Mobile Identification Number (MIN). The crime starts when someone working for a mobile-phone service provider leaks these numbers to grey market operators. The buyer then programs them into new phones which will have the same number as that of the original subscriber.

The accused in the Delhi case used software called Patagonia to clone only CDMA phones (Reliance and Tata Indicom). However, there are software packages that can be used to clone even Global System for Mobile or GSM (e.g. Airtel, Hutch, Idea) phones. In order to clone a GSM phone, knowledge of the International Mobile Equipment Identity (IMEI) or instrument number is sufficient.
well there you have it
http://www.cxotoday.com/cxo/jsp/arti...749&cat_id=909