This read-write setting enables or disables intrusion lock on the port, a security feature under which the port cannot be reconnected once its cable has been disconnected. It's meant to stop someone from unplugging an authorized device and plugging in a different, unauthorized one to gain network access, since the port stays locked until an admin manually clears it. For example, an admin might enable this on ports in an unsecured wiring closet so that pulling the cable permanently disables the port until re-enabled from the management console.