  Recent years have witnessed significant advancements in deep learning-based
3D object detection, leading to its widespread adoption in numerous
applications. As 3D object detectors become increasingly crucial for
security-critical tasks, it is imperative to understand their robustness
against adversarial attacks. This paper presents the first comprehensive
evaluation and analysis of the robustness of LiDAR-based 3D detectors under
adversarial attacks. Specifically, we extend three distinct adversarial attacks
to the 3D object detection task, benchmarking the robustness of
state-of-the-art LiDAR-based 3D object detectors against attacks on the KITTI
and Waymo datasets. We further analyze the relationship between robustness and
detector properties. Additionally, we explore the transferability of
cross-model, cross-task, and cross-data attacks. Thorough experiments on
defensive strategies for 3D detectors are conducted, demonstrating that simple
transformations like flipping provide little help in improving robustness when
the applied transformation strategy is exposed to attackers. \revise{Finally,
we propose balanced adversarial focal training, based on conventional
adversarial training, to strike a balance between accuracy and robustness.} Our
findings will facilitate investigations into understanding and defending
against adversarial attacks on LiDAR-based 3D object detectors, thus advancing
the field. The source code is publicly available at
\url{https://github.com/Eaphan/Robust3DOD}.
