FIGhost: Fluorescent Ink-based Stealthy and Flexible Backdoor Attacks on Physical Traffic Sign Recognition

TL;DR

FIGhost introduces a novel physical-world backdoor attack on traffic sign recognition systems using invisible fluorescent ink triggers activated by UV light, achieving high stealth and robustness against defenses.

Contribution

The paper presents the first fluorescent ink-based backdoor attack for physical traffic signs, enhancing stealth, flexibility, and robustness, and supporting multiple attack objectives.

Findings

Effective against state-of-the-art detectors and VLMs

Maintains robustness under environmental variations

Successfully evades existing defenses

Abstract

Traffic sign recognition (TSR) systems are crucial for autonomous driving but are vulnerable to backdoor attacks. Existing physical backdoor attacks either lack stealth, provide inflexible attack control, or ignore emerging Vision-Large-Language-Models (VLMs). In this paper, we introduce FIGhost, the first physical-world backdoor attack leveraging fluorescent ink as triggers. Fluorescent triggers are invisible under normal conditions and activated stealthily by ultraviolet light, providing superior stealthiness, flexibility, and untraceability. Inspired by real-world graffiti, we derive realistic trigger shapes and enhance their robustness via an interpolation-based fluorescence simulation algorithm. Furthermore, we develop an automated backdoor sample generation method to support three attack objectives. Extensive evaluations in the physical world demonstrate FIGhost's effectiveness against state-of-the-art detectors and VLMs, maintaining robustness under environmental variations and effectively evading existing defenses.