From Threat to Trust: Exploiting Attention Mechanisms for Attacks and Defenses in Cooperative Perception

Cooperative perception (CP) extends detection range and situational awareness in connected and autonomous vehicles by aggregating information from multiple agents. However, attackers can inject fabricated data into shared messages to achieve adversarial attacks. While prior defenses detect object spoofing, object removal attacks remain a serious threat. Nevertheless, prior attacks require unnaturally large perturbations and rely on unrealistic assumptions such as complete knowledge of participant agents, which limits their attack success. In this paper, we present SOMBRA, a stealthy and practical object removal attack exploiting the attentive fusion mechanism in modern CP algorithms. SOMBRA achieves 99% success in both targeted and mass object removal scenarios (a 90%+ improvement over prior art) with less than 1% perturbation strength and no knowledge of benign agents other than the victim. To address the unique vulnerabilities of attentive fusion within CP, we propose LUCIA, a novel trustworthiness-aware attention mechanism that proactively mitigates adversarial features. LUCIA achieves 94.93% success against targeted attacks, reduces mass removal rates by over 90%, restores detection to baseline levels, and lowers defense overhead by 300x compared to prior art. Our contributions set a new state-of-the-art for adversarial attacks and defenses in CP.