TooBad: Backdoor Diffusion Models with Ultra-Low Poison Rate and Imperceptible Trigger
Existing backdoor attacks on diffusion models struggle to simultaneously achieve high efficiency, low poisoning rates, and strong stealthiness. This work proposes TooBad, a novel framework that introduces, for the first time, a trigger optimization mechanism tailored specifically for diffusion models. By integrating fine-tuning with minimal poisoned data injection, TooBad attains over 85% attack success rate with only a 0.5% poisoning ratio; when the poisoning ratio increases to 5%, near-perfect success (≈100%) is achieved within just 3–5 training epochs. The method substantially reduces training overhead while effectively evading state-of-the-art defense mechanisms, thereby offering both potent attack performance and high concealment.