A security seal using a captured lock wire for sealing a device in a manner revealing tampering with the seal includes a locking insert that fits closely within a central cavity of an outer body and is locked within the outer body against removal without visible damage to the insert or the outer body using locking fingers on the insert that cooperate with locking abutments in the cavity that permit insertion of the locking insert into the central cavity but not removal there from. A free end of the lock wire is captured by being threaded through apertures and grooves in the insert and outer body after being secured to a device to be sealed.