Existing black box search methods have achieved high success rate in generating adversarial attacks against NLP models. However, such search methods are inefficient as they do not consider the amount of queries required to generate adversarial attacks. Also, prior attacks do not maintain a consistent search space while comparing different search methods. In this paper, we propose a query efficient attack strategy to generate plausible adversarial examples on text classification and entailment tasks. Our attack jointly leverages attention mechanism and locality sensitive hashing (LSH) to reduce the query count. We demonstrate the efficacy of our approach by comparing our attack with four baselines across three different search spaces. Further, we benchmark our results across the same search space used in prior attacks. In comparison to attacks proposed, on an average, we are able to reduce the query count by 75% across all datasets and target models. We also demonstrate that our attack achieves a higher success rate when compared to prior attacks in a limited query setting.

该研究提出了一种查询效率高的攻击策略来生成文本分类和蕴含任务中的可信对抗性样例，并通过使用注意力机制和局部敏感哈希来减少查询次数。对三个不同的搜索空间使用四种基线进行比较，平均来说我们在所有数据集和目标模型中将查询次数降低了75％。在受限查询设置中，与以前的攻击相比，我们的攻击成功率更高。

黑盒环境下查询效率攻击的强基准