Soft Token Attacks Cannot Reliably Audit Unlearning in Large Language Models

Fuente: arXiv
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Auteurs principaux: Chen, Haokun, Szyller, Sebastian, Xu, Weilin, Himayat, Nageen
Format: Preprint
Publié: 2025
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author Chen, Haokun
Szyller, Sebastian
Xu, Weilin
Himayat, Nageen
author_facet Chen, Haokun
Szyller, Sebastian
Xu, Weilin
Himayat, Nageen
contents Large language models (LLMs) are trained using massive datasets, which often contain undesirable content such as harmful texts, personal information, and copyrighted material. To address this, machine unlearning aims to remove information from trained models. Recent work has shown that soft token attacks (STA) can successfully extract unlearned information from LLMs, but in this work we show that STAs can be an inadequate tool for auditing unlearning. Using common benchmarks such as Who Is Harry Potter? and TOFU, we demonstrate that in a strong auditor setting such attacks can elicit any information from the LLM, regardless of the deployed unlearning algorithm or whether the queried content was originally present in the training corpus. We further show that STA with just a few soft tokens (1-10) can elicit random strings over 400 characters long, indicating that STAs must be used carefully to effectively audit unlearning. Example code can be found at: https://github.com/IntelLabs/LLMart/tree/main/examples/unlearning
format Preprint
id arxiv_https___arxiv_org_abs_2502_15836
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Soft Token Attacks Cannot Reliably Audit Unlearning in Large Language Models
Chen, Haokun
Szyller, Sebastian
Xu, Weilin
Himayat, Nageen
Computation and Language
Artificial Intelligence
Large language models (LLMs) are trained using massive datasets, which often contain undesirable content such as harmful texts, personal information, and copyrighted material. To address this, machine unlearning aims to remove information from trained models. Recent work has shown that soft token attacks (STA) can successfully extract unlearned information from LLMs, but in this work we show that STAs can be an inadequate tool for auditing unlearning. Using common benchmarks such as Who Is Harry Potter? and TOFU, we demonstrate that in a strong auditor setting such attacks can elicit any information from the LLM, regardless of the deployed unlearning algorithm or whether the queried content was originally present in the training corpus. We further show that STA with just a few soft tokens (1-10) can elicit random strings over 400 characters long, indicating that STAs must be used carefully to effectively audit unlearning. Example code can be found at: https://github.com/IntelLabs/LLMart/tree/main/examples/unlearning
title Soft Token Attacks Cannot Reliably Audit Unlearning in Large Language Models
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2502.15836