Hacking Guide to Gsm

Topics: GSM, Mobile phone, Base station Pages: 14 (5756 words) Published: February 27, 2007
Section 1: The Introduction Originally developed as a European standard for mobile telephony, GSM has quickly gained grounds all over the world. However, for much of the world this is still new technology, and therefore there are many people with many questions to ask. One of the ones I most commonly hear from time to time when I idle in Hackers' Lounge is "how do you hack gsm phones?". This is understandable

For much of the world this is still new technology, and there are a lot of people who want to know about all the fun things they can do with these new phones. Well, this tutorial is for all of you. A complete guide for all your gsm hacking needs. Enjoy...

Section 2: How GSM Operates As I've said in past tutorials, in order to hack anything in any sense of the word you have to first understand how it operates. Therefore in this section you will learn the details on GSM to have a better understanding of how it operates. Therefore, you will have a better understanding of how it can be exploited. GSM (Global System for Mobile communication) is fundamentally different from some of it's older counterparts like AMP in the sense that it operates using digital technology, instead of using the traditional analog technology. GSM being a cellular system is of course divided into cells. These cells correspond to their covering area of one trasmitter, or a small collection of transmitters. The size of these cells depend on the power of their transmitter. GSM, as with other cellular systems, uses low power transmitters so that frequencies can be reused efficiently. The frequency band used by a cellular mobile radio system is distributed over a group of cells, which is repeated in all the covering area of an operator. All the radio channels that are available can then be used in each group of cells that form the covering area of an operator. The frequencies that are used then will be reused several cells away. There are four different types of cells that are used. Macrocells, microcells, selective cells, and umbrella cells. Macrocells are large cells that are used for remote and sparsely populated areas. Microcells on the other hand are used for densely populated areas. With using these types of cells in densely populated areas, the number of channels available is increased as well as the capacity of the cells. Transmitters under these types of cells use less power in order to reduce the possibility of interference between neighboring calls. In areas where a full 360 degrees of coverage is not needed, selective cells are used to specify a certain area of coverage.

Umbrella cells are used in correlation with microcells in order to solve the issue with handovers when traversing through microcell areas. The power levels within an umbrella cell is increased compared to the power levels within the microcells that the umbrella cell covers. The cells themselves are grouped into clusters. The number of cells used within a cluster is determined so that the cluster can be repeated continuously within the covering area of an operator. Your typical cluster usually contains either 4, 7, 12, or 21 cells. The number of cells used within a cluster is very important. The smaller the number of cells per cluster is, the bigger the number of channels per cell will be, which will therefore increase the capacity of each cell. The total number of channels used in each cell depends on the number of available channels and the type of cluster used. A balance must be established when setting up these clusters in order to avoid interference with neighboring clusters. Now lets discuss the architecture of the GSM network. A GSM network can be divided into four main parts. The MS (Mobile Station), the BSS (Base Station Subsystem), the NSS (Network and Switching Subsystem), and the OSS (Operation and Support Subsystem). The two main elements of an MS is the terminal, and the SIM (Subscriber Identity Module). There are different types of terminals within...
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