A portable communication device comprises a GPS module for determining the present position, an electronic compass module for detecting an azimuth, a display, and a wireless communicator. The system retrieves labels assigned to the identified similar images and selectively concatenates the extracted labels. The coils provide a rotating magnetic field having approximately constant amplitude regardless of orientation with respect to the transponder. The packet in the legacy packet format is reformatted to yield a target packet in a non-legacy packet format based, at least in part, on the non-legacy communication protocol. Such computer system defense techniques can also be augmented to automatically optimize the disruptive communications sent to the attackers.