🤖 AI Summary
This work addresses the vulnerability of pretrained vision-language models to adversarial perturbations under zero-shot settings, where existing adversarial fine-tuning methods often degrade cross-modal alignment and impair generalization. To mitigate this issue, the authors propose an Alignment-Guided Fine-Tuning (AGFT) framework that preserves semantic alignment between visual and textual representations while enhancing robustness. AGFT leverages the soft prediction distribution of the original model as an alignment guide, integrates text-guided adversarial training, and employs a temperature-scaling calibration mechanism. Experimental results demonstrate that AGFT substantially outperforms current approaches across multiple zero-shot benchmarks, achieving significantly improved adversarial robustness without compromising zero-shot generalization capability.
📝 Abstract
Pre-trained vision-language models (VLMs) exhibit strong zero-shot generalization but remain vulnerable to adversarial perturbations. Existing classification-guided adversarial fine-tuning methods often disrupt pre-trained cross-modal alignment, weakening visual-textual correspondence and degrading zero-shot performance. In this paper, we propose an Alignment-Guided Fine-Tuning (AGFT) framework that enhances zero-shot adversarial robustness while preserving the cross-modal semantic structure. Unlike label-based methods that rely on hard labels and fail to maintain the relative relationships between image and text, AGFT leverages the probabilistic predictions of the original model for text-guided adversarial training, which aligns adversarial visual features with textual embeddings via soft alignment distributions, improving zero-shot adversarial robustness. To address structural discrepancies introduced by fine-tuning, we introduce a distribution consistency calibration mechanism that adjusts the robust model output to match a temperature-scaled version of the pre-trained model predictions. Extensive experiments across multiple zero-shot benchmarks demonstrate that AGFT outperforms state-of-the-art methods while significantly improving zero-shot adversarial robustness.