A system for automatically disarming an intrusion detection system protecting a premises and having at least an armed state of operation and a disarmed state of operation, the system for automatically disarming the intrusion detection system including an intrusion detection system state of operation ascertainer operable for receiving an indication of activation of an armed state of operation of the intrusion detection system; and a registered mobile communicator proximity detector communicating with the intrusion detection system state of operation ascertainer and operable, responsive to receiving the indication of activation of the armed state of operation by the intrusion detection system state of operation ascertainer for ascertaining at least a subset of a multiplicity of registered mobile communicators which are located in a vicinity of the premises during an activation time of the armed state of operation and for deactivating the subset of the multiplicity of registered mobile communicators.