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RESEARCH PAPER / 2025-10-01

Backdoor Attacks Against Speech Language Models

Alexandrine Fortier, Thomas Thebaud, Jesús Villalba, ★ Najim Dehak ...Full author list in the original paper.

Johns Hopkins University +4 · arXiv

Affiliations: Johns Hopkins University, Ecole de technologie sup, us Villalba, Department of Electrical and Computer Engineering, Department of Software and IT Engineering

Abstract

Large Language Models (LLMs) and their multimodal extensions are becoming increasingly popular. One common approach to enable multimodality is to cascade domain-specific encoders with an LLM, making the resulting model inherit vulnerabilities from all of its components. In this work, we present the first systematic study of audio backdoor attacks against speech language models. We demonstrate its effectiveness across four speech encoders and three datasets, covering four tasks: automatic speech recognition (ASR), speech emotion recognition, and gender and age prediction. The attack consistently achieves high success rates, ranging from 90.76% to 99.41%. To better understand how backdoors propagate, we conduct a component-wise analysis to identify the most vulnerable stages of the pipeline. Finally, we propose a fine-tuning-based defense that mitigates the threat of poisoned pretrained encoders.

The following analysis is generated by AI and may contain errors. It is separate from the authors’ abstract and is not peer review.

Research summary

This paper presents the first systematic study of backdoor attacks against speech language models, revealing critical vulnerabilities and offering insights into the propagation of such attacks within multimodal architectures. The comprehensive methodology and rigorous experimental evaluation contribute significantly to the understanding of security in machine learning systems, particularly in the context of speech processing.

Methodology

The methodology presented in this paper is robust, featuring a systematic approach to backdoor attacks against speech language models. The authors effectively utilize a natural-sounding trigger and a well-defined poisoning strategy to evaluate the vulnerabilities of various components within the SpeechLLM architecture. The component-wise analysis is particularly commendable, as it isolates the contributions of different modules, providing insights into the propagation of backdoors. However, the focus on a single type of trigger and poisoning strategy may limit the generalizability of the findings.

Results & evaluation

The experiments are comprehensive, covering multiple datasets and tasks, which enhances the validity of the results. The authors report high attack effectiveness rates across various tasks, demonstrating the robustness of their approach. The inclusion of a fine-tuning defense strategy adds depth to the experimental evaluation, although the performance drop when fine-tuning on a new dataset raises questions about the practicality of this defense. The results are well-presented, with clear metrics and comparisons across different encoder architectures.

Reproducibility

The paper provides a GitHub repository link, which is beneficial for reproducibility. However, the details regarding the implementation of the attacks and the specific configurations used for the experiments could be more thoroughly documented to facilitate easier replication by other researchers. The methodology section is detailed, but additional clarity on hyperparameters and training settings would enhance reproducibility.

Limitations

The study is limited by its focus on a single type of backdoor attack and a specific trigger, which may not encompass the full range of potential vulnerabilities in speech language models. Additionally, the findings may not generalize to other multimodal models outside of the SpeechLLM framework. The reliance on clean data for fine-tuning as a defense mechanism also presents practical challenges, as access to clean datasets may not always be feasible.

Broader impact

The implications of this research are significant, as it highlights the vulnerabilities of speech language models to backdoor attacks, which could have serious consequences in real-world applications such as voice recognition systems and automated customer service. The insights gained from this study could inform the development of more secure models and defenses against such attacks, ultimately contributing to safer AI systems. This paper presents the first systematic study of backdoor attacks against speech language models, revealing critical vulnerabilities and offering insights into the propagation of such attacks within multimodal architectures. The comprehensive methodology and rigorous experimental evaluation contribute significantly to the understanding of security in machine learning systems, particularly in the context of speech processing.

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