(for a broader academic view of mobile security from that era)
This is required for updating or changing the firmware on the device, providing a layer of security for deeper system modifications. Practical Use and Compatibility universal mastercode v.04 by darmiles
The main appeal of the Universal MasterCode v.0.4 was its wide compatibility and free-of-charge nature. It reportedly worked perfectly with modems from a vast array of brands and operators, including: (for a broader academic view of mobile security