A sensor for a security system is disclosed to detect intrusions at one or more predetermined locations wherein each location includes a moveable member which must be moved in order to intrude the location. The system includes a fiber network routed in close proximity to one or more locations. The sensor comprises a sensor housing for being disposed at a location to detect a predetermined movement of the moveable member from a secure position to an unsecured position, and means for mounting the sensor housing in a stationary position at the location without a physical connection to the moveable member. The sensor housing includes a fiber inlet and a fiber outlet, and a fiber chamber for receiving a predetermined sensor fiber of the fiber network being routed through the sensor housing. The sensor has a sensor actuator for engaging the sensor fiber to generate an intrusion signal upon detecting predetermined movement of the moveable member, and causing the intrusion signal to be transmitted along the sensor fiber to a processor whereby the intrusion and location of the intrusion may be determined by the processor. Preferably, the sensor includes a magnetic actuator having a magnetic attraction to the moveable members whose interruption causes activation of the sensor and generation of the intrusion signal.