Abstract: A computer implemented security method for a set of internet-of-things (IoT) devices, the set of devices comprising network-connected sensors and actuators, wherein a data repository stores data about the devices, actions performable by each of the devices and one or more network attacks to which at least a subset of the devices are susceptible, the method comprising: defining, for each network attack, one or more responsive actions for the attack, each responsive action identifying one or more performable actions for performance by one or more devices to mitigate the attack; detecting a device in a compromised state, the compromised state being determined based on a threshold number of occurrences of an attack perpetrated against the device; selecting responsive actions for the perpetrated attack; and triggering the responsive actions to mitigate the perpetrated attack.