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Title: Cell phone cloning: A perspective on GSM security Authors: 1. Ramesh Singh, Senior Technical Director, National Informatics Center, New Delhi, India (www.home.nic.in) 2. Preeti Bhargava, undergraduate student, Delhi College of Engineering, New Delhi, India (www.dce.edu) 3. Samta Kain, undergraduate student, Delhi College of Engineering, New Delhi, India (www.dce.edu)

Mr. Steve Andrewsalmost got a heart attack after seeing his monthly mobile bill for $8000. He contacted his cell phone provider to let them know that somebody else is also using his cellphone without his knowledge but they weren’t interested in helping him and asked him to pay. Are your mobile phone bills unexpectedly high like that of Mr. Andrews? Then there is a chance that you might be a victim of "mobilecloning". It is also known as cell phone piracy and has been taking place throughout the world since decades. 1. What is Cell Phone Cloning? Cell phone cloning or mobile cloning is copying the identity of one mobile telephone to another mobile telephone. Usually this is done for the purpose of making fraudulent telephone calls. The bill for the calls goes to the legitimate subscriber. 2. How is a phonecloned? The “cloning” occurs when the account number of a victim telephone user is stolen and reprogrammed into another cellular telephone. Every cell phone is supposed to have a unique factory-set Electronic Serial Number (ESN) and Mobile Identification Number (MIN). A cloned cell phone is one that has been reprogrammed to transmit the ESN and MIN belonging to another (legitimate) cell phone.Unscrupulous people can obtain valid ESN/MIN combinations by illegally monitoring the radio wave transmissions from the cell phones of legitimate subscribers. After cloning, both the legitimate and the fraudulent cell phones have the same ESN/MIN combination and cellular systems cannot distinguish the cloned cell phone from the legitimate one. The legitimate phone user then gets billed for thecloned phone's calls. Cellular thieves can capture ESN/MINs using devices such as cell phone ESN reader or digital data interpreters (DDI). An ESN reader is a cellular telephone receiver designed to monitor the control channel. The ESN reader captures the pair as it is being broadcast from a cellular telephone to a cell site and stores the information into its memory. What makes this possible is thefact that each time your cellular telephone is turned on or used; it transmits the pair to the local cellular site and establishes a talk channel. It also transmits the pair when it is relocated from one cell site to another. DDIs are devices specially manufactured to intercept ESN/MINs. By simply sitting near busy roads where the volume of cellular traffic is high, cellular thieves monitoring theradio wave transmissions from the cell phones of legitimate subscribers can capture ESN/MIN pair. Numbers can be recorded by hand, one-by-one, or stored in the box and later downloaded to a computer. ESN/MIN readers can also be used from inside an offender’s home, office, or hotel room, increasing the difficulty of detection. Softwares are available to clone even CDMA and GSM phones. CDMA usesspread spectrum techniques for transmitting voice or data over the air. Rather than dividing the radio frequency spectrum into separate user channels by frequency slices or time slots, spread spectrum technology separates users by assigning them digital codes within the same broad spectrum. GSM is a digital mobile telephone system that is widely used in Europe and other parts of the world. GSM uses avariation of TDMA and is the most widely used of the three digital wireless telephone technologies. GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. The ubiquity of the GSM standard makes international roaming very common between mobile phone operators, enabling subscribers to use their phones in many parts of the...