Apparatus and methods are presented for protecting data in microcontrollers from both malicious software processes running inside the device as well as from unauthorized attempts to read the data from an external data bus and/or external memory. An illustrative embodiment of the invention accomplishes these security improvements, in part, by utilizing an enhanced memory management unit (MMU). The enhanced MMU is configured to prevent one software process running on the microcontroller from accessing data associated with a different software process running on the same microcontroller. Moreover, data transmitted over an external data bus or stored in an external memory is encrypted, thereby reducing the chances that unauthorized users will gain exploitable information from this data.