When a notification indicating the abnormality is received by a portable electronic device, an operator identification operating section identifies the operator of the portable electronic device as a user who is to receive the notification or a person having some connection with the user, based on a physical feature peculiar to an individual. If the operator is an authorized user, a message operating section makes a radio transceiver unit to receive trespass-related data including specific information specifying the place of where the behavior occurs. A security object positional information displaying section displays the specific information included in the trespass-related data on a screen of the portable electronic device. The user can notify to the police and the like based on the display. The present invention is applicable to any security system.