Ever give much thought to the little piece of plastic in your mobile phone? No? That's mostly because SIM cards are greatly misunderstood and perform their function extremely well. So what is it that I am getting at?
The SIM card is primarily your network identifier, it allows your device to identify and authorize itself on the home network. To do this it makes use of special security keys and algorithms. What you may not have known is that the SIM is the master of the phone, it has to possibility to dictate what the device should do.
The SIM can instruct the device to send an SMS, initiate a call, launch a web-browser, send a USSD, get network statistics including positional/location values and so much more. All this without user intervention or even consent!
Interested? In my proceeding posts I will dig further into how the mechanism around this work and how secure they may be.