An anti-theft device for protecting objects and vehicles, includes a housing that is attachable to or permanently affixed to an object or vehicle to be secured, wherein the attachment means is accessible only through a lockable access door of the housing. A flexible conducting securing cable serves as a conductor in an alarm circuit and has one end fixed to the housing and a free end provided with a fitting for insertion into the housing that is retained by a retainer and a lock mechanism in the housing. First and second switches are provided in the alarm circuit wherein the first switch is normally open and is closed when the housing is attached to the object, while the second switch is normally open and is closed when the free end of the cable is inserted into the retainer. The alarm circuit is armed when both the first and second switches are closed, and subsequent opening of the first switch or tampering of the conduction path formed by the conducting securing cable activates an alarm.