Is the modem chip designed so that the nothing can alter the radio modem's own software? This program should not be updatable.
This because any NSA, KGB, New Zelander snoop force, or LAPD contractor with the right information from the manufacturer could upload a nasty custom modem firmware to do bad stuff even if the modem can't force its way with the main processor. Is there a way to checksum the modem firmware every time we boot?