IMSI-catcher
An IMSI catcher is essentially a false mobile tower acting between the target mobile phone(s) and the service providers real towers. As such it is considered a Man In the Middle (MITM) attack. It is used as an eavesdropping device used for interception and tracking of cellular phones and usually is undetectable for the users of mobile phones. Such a virtual base transceiver station (VBTS) is a device for identifying the International Mobile Subscriber Identity (IMSI) of a nearby GSM mobile phone and intercepting its calls. It was patented and first commercialized by Rohde & Schwarz, although it would be hard to maintain such a patent, since in reality it is just a modified cell tower with a malicious operator. On 24 January 2012, the Court of Appeal of England and Wales held that the patent is invalid for obviousness.
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