SPI, or Serial Peripheral Interface, is a short-distance serial bus used by a controller to exchange data with peripheral devices such as flash memory. In embedded systems, it often carries boot firmware and configuration data between the main processor and the storage chip, making it a basic part of how a device starts and functions.
SPI matters in cyber security because access to this bus can expose firmware without removing the chip from the board. Analysts use in-circuit SPI reads for repair, recovery, and reverse engineering, but attackers with physical access may also use the same path to copy or modify sensitive code. If the bus is weakly protected, it can weaken the device’s trust chain and reveal implementation details, update logic, or stored secrets. Defenders reduce risk with locked-down service interfaces, authenticated updates, and hardware designs that make unauthorized reads or writes harder.