Nowadays mobile networks are the most dynamic part of critical communication infrastructures and the key instrument used to perform daily activities ranging from voice and text messaging to providing signaling for emergency services and critical infrastructure. Regardless of what security assurances mobile network operators provide, there is plenty of hard evidence that in fact shows how vulnerable these systems are. Lately, it seems like a common occurrence when private telephone conversations or pictures of government officials, celebrities and business leaders appear on the Internet, even though these individuals usually take extra precautions when it comes to their personal privacy and safety. In many instances, a common misconception is that security breaches like these are very complicated and expensive to execute and can only be accomplished by high-ranking security intelligence agencies, organized crime or the most sophisticated hackers. This perception is understandable, since most people are trained to view a mobile communication network as a system made up of only the most cutting edge technologies. However, in reality a telecommunications network is a complex system built on subsystems that each have different technological levels, with the security
