defense arXiv Mar 27, 2026 · 10d ago
Mujtaba Hussain Mirza, Antonio D'Orazio, Odelia Melamed et al. · Sapienza University of Rome · Weizmann Institute of Science
Training-free test-time defense using energy minimization to purify adversarial inputs for classifiers and vision-language models
Input Manipulation Attack visionmultimodalnlp
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 .
vlm cnn transformer multimodal Sapienza University of Rome · Weizmann Institute of Science