GPIO stands for general-purpose input/output. These are configurable pins on a board or chip that software can read as digital input or drive as digital output. A pin may detect a button press, sensor state, or jumper signal, or it may switch an LED, relay, or other external device on and off.
In cyber security, GPIO matters because it is a direct bridge between software and physical hardware. On embedded devices and single-board computers, attackers may abuse GPIO to trigger hidden functions, bypass software controls, or manipulate attached components. Defenders use the same interface for diagnostics, tamper detection, and hardware controls, but they often restrict access with permissions, firmware settings, or enclosure design. If GPIO is exposed without protection, it can become a low-level path around otherwise locked-down software.