arXiv Machine Learning By Yixin Tan, Jiayang Liu, Lu Sun, Yuke Hu, Zheng Li, Rui Wen

When Routing Reveals Membership: Privacy Leakage from MoE Router Telemetry

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The paper demonstrates that routing information logged by Mixture-of-Experts (MoE) language models can be used to infer whether a specific example was part of a model’s fine‑tuning data. By combining router telemetry with standard output signals and training a membership classifier on shadow models, the authors achieve higher true‑positive rates across multiple MoE architectures and data domains. The study shows that this privacy leakage persists under various fine‑tuning regimes and even with limited telemetry, indicating that router logs can become an additional privacy risk for deployed MoE models.

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