Abstract
Vision Transformers (ViTs) remain vulnerable to localized adversarial attacks, such as adversarial patches, while recent test-time defenses mitigate them by suppressing image tokens with abnormally high attention scores. These defenses exploit a strong coupling between attention and adversarial effectiveness: adversarial tokens often need to attract substantial attention to influence the prediction.
We introduce adversarial decoys, independently optimized image patches that redirect the attention, and therefore related defenses, toward selected target tokens. Rather than jointly optimizing misclassifications and defense evasion, our approach decouples the two objectives: the original adversarial region induces the incorrect prediction, while a separate decoy manipulates the attention ranking used by the defense.
A layer-wise objective increases target-token attention and promotes these tokens above competing non-target ones.
Since the decoy is optimized independently of the underlying attack, the method is attack-agnostic and can be easily integrated with any existing adversarial patch attack. Experiments on ImageNet across multiple ViT architectures and attacks show that decoys can redirect high attention scores away from the true adversarial region while preserving much of the attack effectiveness. These results reveal a fundamental limitation of using attention magnitude as an indicator of adversarial relevance.
Blogger's Review: This research presents an innovative approach in the field of adversarial attacks, effectively challenging existing attention-based defense mechanisms through the introduction of adversarial decoys. This method not only enhances the stealth of adversarial attacks but also provides new insights for future defense strategy designs, warranting attention.