Zhengyu Zhao


2025

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An Optimizable Suffix Is Worth A Thousand Templates: Efficient Black-box Jailbreaking without Affirmative Phrases via LLM as Optimizer
Weipeng Jiang | Zhenting Wang | Juan Zhai | Shiqing Ma | Zhengyu Zhao | Chao Shen
Findings of the Association for Computational Linguistics: NAACL 2025

Despite prior safety alignment efforts, LLMs can still generate harmful and unethical content when subjected to jailbreaking attacks. Existing jailbreaking methods fall into two main categories: template-based and optimization-based methods. The former requires significant manual effort and domain knowledge, while the latter, exemplified by GCG, which seeks to maximize the likelihood of harmful LLM outputs through token-level optimization, also encounters several limitations: requiring white-box access, necessitating pre-constructed affirmative phrase, and suffering from low efficiency. This paper introduces ECLIPSE, a novel and efficient black-box jailbreaking method with optimizable suffixes. We employ task prompts to translate jailbreaking objectives into natural language instructions, guiding LLMs to generate adversarial suffixes for malicious queries. A harmfulness scorer provides continuous feedback, enabling LLM self-reflection and iterative optimization to autonomously produce effective suffixes. Experimental results demonstrate that ECLIPSE achieves an average attack success rate (ASR) of 0.92 across three open-source LLMs and GPT-3.5-Turbo, significantly outperforming GCG by 2.4 times. Moreover, ECLIPSE matches template-based methods in ASR while substantially reducing average attack overhead by 83%, offering superior attack efficiency.

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Typographic Attacks in a Multi-Image Setting
Xiaomeng Wang | Zhengyu Zhao | Martha Larson
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)

Large Vision-Language Models (LVLMs) are susceptible to typographic attacks, which are misclassifications caused by an attack text that is added to an image. In this paper, we introduce a multi-image setting for studying typographic attacks, broadening the current emphasis of the literature on attacking individual images. Specifically, our focus is on attacking image sets without repeating the attack query. Such non-repeating attacks are stealthier, as they are more likely to evade a gatekeeper than attacks that repeat the same attack text. We introduce two attack strategies for the multi-image setting, leveraging the difficulty of the target image, the strength of the attack text, and text-image similarity. Our text-image similarity approach improves attack success rates by 21% over random, non-specific methods on the CLIP model using ImageNet while maintaining stealth in a multi-image scenario. An additional experiment demonstrates transferability, i.e., text-image similarity calculated using CLIP transfers when attacking InstructBLIP.

2024

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Composite Backdoor Attacks Against Large Language Models
Hai Huang | Zhengyu Zhao | Michael Backes | Yun Shen | Yang Zhang
Findings of the Association for Computational Linguistics: NAACL 2024

Large language models (LLMs) have demonstrated superior performance compared to previous methods on various tasks, and often serve as the foundation models for many researches and services. However, the untrustworthy third-party LLMs may covertly introduce vulnerabilities for downstream tasks. In this paper, we explore the vulnerability of LLMs through the lens of backdoor attacks. Different from existing backdoor attacks against LLMs, ours scatters multiple trigger keys in different prompt components. Such a Composite Backdoor Attack (CBA) is shown to be stealthier than implanting the same multiple trigger keys in only a single component. CBA ensures that the backdoor is activated only when all trigger keys appear. Our experiments demonstrate that CBA is effective in both natural language processing (NLP) and multimodal tasks. For instance, with 3% poisoning samples against the LLaMA-7B model on the Emotion dataset, our attack achieves a 100% Attack Success Rate (ASR) with a False Triggered Rate (FTR) below 2.06% and negligible model accuracy degradation. Our work highlights the necessity of increased security research on the trustworthiness of foundation LLMs.

2021

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What Did You Refer to? Evaluating Co-References in Dialogue
Wei-Nan Zhang | Yue Zhang | Hanlin Tang | Zhengyu Zhao | Caihai Zhu | Ting Liu
Findings of the Association for Computational Linguistics: ACL-IJCNLP 2021

2020

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Profile Consistency Identification for Open-domain Dialogue Agents
Haoyu Song | Yan Wang | Wei-Nan Zhang | Zhengyu Zhao | Ting Liu | Xiaojiang Liu
Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP)

Maintaining a consistent attribute profile is crucial for dialogue agents to naturally converse with humans. Existing studies on improving attribute consistency mainly explored how to incorporate attribute information in the responses, but few efforts have been made to identify the consistency relations between response and attribute profile. To facilitate the study of profile consistency identification, we create a large-scale human-annotated dataset with over 110K single-turn conversations and their key-value attribute profiles. Explicit relation between response and profile is manually labeled. We also propose a key-value structure information enriched BERT model to identify the profile consistency, and it gained improvements over strong baselines. Further evaluations on downstream tasks demonstrate that the profile consistency identification model is conducive for improving dialogue consistency.