GSM

GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard set developed by the European Telecommunications Standards Institute (ETSI) to describe technologies for second generation (2G) digital cellular networks.

GSM features

Key management is independent of equipment it allows the subscribers to be able change handsets without compromising security.

Subscriber identity protection so that it will not be easy to identify the user of the system intercepting a user data.

Detection of compromised equipment it is a detection mechanism whether a mobile device was compromised or not.

Subscriber authentication so that the operator knows for billing purposes who is using the system.

Signaling and user data protecting allows data channels to be protected over the radio path.

GSM threats

Eavesdropping - The capability of an intruder to intercept traffic and signaling information associated to other users. The required equipment is a modified mobile phone.

Impersonation of a user - This is the capability of sending rogue data and/or signaling messages to the network with the intent of making them appear from another user. This again only requires a modified mobile phone.

Impersonation of the network - This is the capability of sending rogue data and/or signaling messages to another user with the intent of making them appear from a genuine network. This
requires a modified BTS.

MITM – Man-In-The-Middle - This is the capability of an attacker to put itself between the network and the legitimate user in order to eavesdrop, modify, delete, re-order, re-play and spoof signaling data between the two parties. This requires a modified BTS in conjunction with a modified mobile phone.

Network Authentication Compromise - The intruder possesses a compromised authentication
vector (challenge-response pairs, cipher keys, integrity key, etc)

GSM threats solution

The GSM security design is weak to the extend that not much improvements could be done to fight against these threats. As communication is done through wireless, (which means that the transmission and reception of messages is conveyed through the air) there are security limitations in mobile communication stem. One of the precaution is anonymity. It helps to make it difficult to identify the user of the system. Anonymity is provided by the use of temporary identifiers. When a new GSM subscriber switches on his/her mobile device for the first time, the real identity which is also known as the International Mobile User/Subscriber Identity (IMUI/IMSI) is used and a Temporary Mobile User/Subscriber Identity (TMUI/TMSI) is then issued to this subscriber. From then on, the temporary identifier is used. The only way of determining the temporary identity being used is by tracking the user. Therefore, the use of TMUI, prevents the recognition of a GSM user by a potential eavesdropper or hacker.