  Deep neural networks (DNNs) are increasingly integrated into LiDAR (Light
Detection and Ranging)-based perception systems for autonomous vehicles (AVs),
requiring robust performance under adversarial conditions. We aim to address
the challenge of LiDAR spoofing attacks, where attackers inject fake objects
into LiDAR data and fool AVs to misinterpret their environment and make
erroneous decisions. However, current defense algorithms predominantly depend
on perception outputs (i.e., bounding boxes) thus face limitations in detecting
attackers given the bounding boxes are generated by imperfect perception models
processing limited points, acquired based on the ego vehicle's viewpoint. To
overcome these limitations, we propose a novel framework, named ADoPT (Anomaly
Detection based on Point-level Temporal consistency), which quantitatively
measures temporal consistency across consecutive frames and identifies abnormal
objects based on the coherency of point clusters. In our evaluation using the
nuScenes dataset, our algorithm effectively counters various LiDAR spoofing
attacks, achieving a low (< 10%) false positive ratio (FPR) and high (> 85%)
true positive ratio (TPR), outperforming existing state-of-the-art defense
methods, CARLO and 3D-TC2. Furthermore, our evaluation demonstrates the
promising potential for accurate attack detection across various road
environments.
