The interfaces in embedded systems are potential points of attack. This applies to interfaces on all levels of the ISO/OSI layer model and all transmission media used. If access via these interfaces is not controlled or if the control mechanisms used are too weak, attackers could infiltrate the system, read and write data without authorisation, and initiate subsequent attacks. They could also connect spying or sabotage devices such as miniaturised controllers or data loggers without anyone noticing.

If such devices are connected to a system's I/O ports at the microcontroller level, signals could be fed into the I/O registers via the I/O lines or output signals could be recorded.

If there is a reset input, attackers could control it and temporarily shut down the system.