Here’s a Free Lunch: Sanitizing Backdoored Models with Model Merge

Ansh Arora, Xuanli He, Maximilian Mozes, Srinibas Swain, Mark Dras, Qiongkai Xu


Abstract
The democratization of pre-trained language models through open-source initiatives has rapidly advanced innovation and expanded access to cutting-edge technologies. However, this openness also brings significant security risks, including backdoor attacks, where hidden malicious behaviors are triggered by specific inputs, compromising natural language processing (NLP) system integrity and reliability. This paper suggests that merging a backdoored model with other homogeneous models can significantly remediate backdoor vulnerabilities even if such models are not entirely secure. In our experiments, we verify our hypothesis on various models (BERT-Base, RoBERTa-Large, Llama2-7B, and Mistral-7B) and datasets (SST-2, OLID, AG News, and QNLI). Compared to multiple advanced defensive approaches, our method offers an effective and efficient inference-stage defense against backdoor attacks on classification and instruction-tuned tasks without additional resources or specific knowledge. Our approach consistently outperforms recent advanced baselines, leading to an average of about 75% reduction in the attack success rate. Since model merging has been an established approach for improving model performance, the extra advantage it provides regarding defense can be seen as a cost-free bonus.
Anthology ID:
2024.findings-acl.894
Volume:
Findings of the Association for Computational Linguistics ACL 2024
Month:
August
Year:
2024
Address:
Bangkok, Thailand and virtual meeting
Editors:
Lun-Wei Ku, Andre Martins, Vivek Srikumar
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
15059–15075
Language:
URL:
https://aclanthology.org/2024.findings-acl.894
DOI:
Bibkey:
Cite (ACL):
Ansh Arora, Xuanli He, Maximilian Mozes, Srinibas Swain, Mark Dras, and Qiongkai Xu. 2024. Here’s a Free Lunch: Sanitizing Backdoored Models with Model Merge. In Findings of the Association for Computational Linguistics ACL 2024, pages 15059–15075, Bangkok, Thailand and virtual meeting. Association for Computational Linguistics.
Cite (Informal):
Here’s a Free Lunch: Sanitizing Backdoored Models with Model Merge (Arora et al., Findings 2024)
Copy Citation:
PDF:
https://aclanthology.org/2024.findings-acl.894.pdf