DALA: A Distribution-Aware LoRA-Based Adversarial Attack against Language Models

Language models (LMs) can be manipulated by adversarial attacks, which introduce subtle perturbations to input data. While recent attack methods can achieve a relatively high attack success rate (ASR), we've observed that the generated adversarial examples have a different data distribution compared with the original examples. Specifically, these adversarial examples exhibit reduced confidence levels and greater divergence from the training data distribution. Consequently, they are easy to detect using straightforward detection methods, diminishing the efficacy of such attacks. To address this issue, we propose a Distribution-Aware LoRA-based Adversarial Attack (DALA) method. DALA considers distribution shifts of adversarial examples to improve the attack's effectiveness under detection methods. We further design a novel evaluation metric, the Non-detectable Attack Success Rate (NASR), which integrates both ASR and detectability for the attack task. We conduct experiments on four widely used datasets to validate the attack effectiveness and transferability of adversarial examples generated by DALA against both the white-box BERT-base model and the black-box LLaMA2-7b model. Our codes are available at https://anonymous.4open.science/r/DALA-A16D/.