Actually, for a long time now it was bothersome to me that malware would be able to write itself into PROMs that allow being flash written (such as computer BIOs and DvD drive controller chips, home TV system and camera control chips and even automobile computer and related ECU control chips).
Seems that all such chip systems which are flash-able should now employ hardware write protection. On a chip, this could just be a small physical piece on the chip that must be manually moved/removed to enable firmware modification.