Nonlocalizable Jamming with Curving Beams

Radio jamming is a significant security threat to critical wireless systems, potentially disrupting communications, navigation, and public-safety operations. Modern defenses rely on direction-of-arrival (DoA) localization and array nulling to locate and suppress interferers. These methods assume that incident wavefronts are approximately planar so that relative phase measurements across an array accurately indicate bearing. In this paper, we show that an adversary can fool DoA-based localization and nulling by transmitting curving beams. Such beams can create interference at a victim and induce a falsified DoA. This both conceals the adversary's true location and enables her to jam into the victim's main lobe. We investigate how various curving beam parameters affect DoA estimation and use these insights to describe how an adversary can search for optimal curving beams for her attack. We experimentally evaluate the attack with a millimeter wave testbed, showing that a curving beam jammer can increase bit error rate by three orders of magnitude. We find that the curving beams can successfully spoof both direct phase measurements and receive beamforming.