A security system comprises a computer network and a plurality of sensors each connected to the computer network at a respective network address and each generating sensing data. A managing component is connected with the network and communicates with the sensors by access thereof through the associated network address on the network, and processes sensor information received from said sensors. The managing component has a display with an interface screen showing to a user all the sensors in the security system, and an input device through which the user can enter interactive instructions to the managing component. The managing component controls communications to and from the sensors and has a rules engine storing rules therein. Each of the rules being associated with a respective device on the network, and causing the managing computer to take an action in response to output from at least one of the devices.