Practical Reflection Manipulation on mmWave-Based Physical Intrusion Detection

mmWave sensing has emerged as a promising technique for physical intrusion detection, offering reliable performance across diverse environments and benefiting from the growing availability of low-cost commodity mmWave devices. However, its integration also raises critical security concerns, particularly on vulner-abilities to signal manipulation attacks. While previous studies have demonstrated the feasibility of such attacks using advanced software-defined radios, practical and low-cost signal manipulation attacks remain largely unexplored, highlighting a significant research gap in understanding the security of mmWave-based physical intrusion detection systems. In this study, we identify and experimentally evaluate a novel reflection manipulation attack that costs less than 100 USD to implement. Specifically, an array of low-cost passive corner reflectors is mounted on the intruder. The reflectors are uniformly arranged in a circular formation and rotated by a motor. This simple yet effective design manipulates the CFAR detection threshold, thereby concealing both the intruder and the reflectors. Experimental results confirm that the attack is highly effective under certain system configurations but fails under others. Motivated by this observation, we further propose several defenses to effectively mitigate the threat posed by the attack.