🤖 AI Summary
Large vision-language models exhibit insufficient robustness under adversarial perturbations, limiting their practical deployment. This work proposes ET3, a lightweight, training-free test-time defense method that, for the first time, introduces an energy minimization mechanism into the test phase of vision-language models. By leveraging energy-guided input transformation, ET3 enhances model robustness while, under reasonable assumptions, providing theoretical guarantees for classification correctness. Experimental results demonstrate that ET3 significantly outperforms existing test-time defenses across multiple tasks—including image classification, image captioning, and visual question answering—effectively improving adversarial robustness without requiring retraining or architectural modifications.
📝 Abstract
Despite the rapid progress in multimodal models and Large Visual-Language Models (LVLM), they remain highly susceptible to adversarial perturbations, raising serious concerns about their reliability in real-world use. While adversarial training has become the leading paradigm for building models that are robust to adversarial attacks, Test-Time Transformations (TTT) have emerged as a promising strategy to boost robustness at inference.In light of this, we propose Energy-Guided Test-Time Transformation (ET3), a lightweight, training-free defense that enhances the robustness by minimizing the energy of the input samples.Our method is grounded in a theory that proves our transformation succeeds in classification under reasonable assumptions. We present extensive experiments demonstrating that ET3 provides a strong defense for classifiers, zero-shot classification with CLIP, and also for boosting the robustness of LVLMs in tasks such as Image Captioning and Visual Question Answering. Code is available at github.com/OmnAI-Lab/Energy-Guided-Test-Time-Defense .