EL-MIA: Quantifying Membership Inference Risks of Sensitive Entities in LLMs

Ali Satvaty, Suzan Verberne, Fatih Turkmen


Abstract
Membership inference attacks (MIA) aim to infer whether a particular data point is part of the training dataset of a model. In this paper, we propose a new task in the context of LLM privacy: entity-level discovery of membership risk focused on sensitive information (PII, credit card numbers, etc). Existing methods for MIA can detect the presence of entire prompts or documents in the LLM training data, but they fail to capture risks at a finer granularity. We propose the “EL-MIA” framework for auditing entity-level membership risks in LLMs. We construct a benchmark dataset for the evaluation of MIA methods on this task. Using this benchmark, we conduct a systematic comparison of existing MIA techniques as well as two newly proposed methods. We provide a comprehensive analysis of the results, trying to explain the relation of the entity level MIA susceptability with the model scale, training epochs, and other surface level factors. Our findings reveal that existing MIA methods are limited when it comes to entity-level membership inference of the sensitive attributes, while this susceptibility can be outlined with relatively straightforward methods, highlighting the need for stronger adversaries to stress test the provided threat model.
Anthology ID:
2026.lrec-1.362
Volume:
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Month:
May
Year:
2026
Address:
Palma de Mallorca, Spain
Editors:
Stelios Piperidis, Núria Bel, Henk van den Heuvel, Nancy Ide, Simon Krek, Antonio Toral
Venue:
LREC
SIG:
Publisher:
ELRA Language Resource Association
Note:
Pages:
4611–4625
Language:
External URL:
https://lrec.elra.info/lrec2026-main-362
DOI:
10.63317/59k6vkt3biya
Bibkey:
Cite (ACL):
Ali Satvaty, Suzan Verberne, and Fatih Turkmen. 2026. EL-MIA: Quantifying Membership Inference Risks of Sensitive Entities in LLMs. In Proceedings of the Fifteenth Language Resources and Evaluation Conference, pages 4611–4625, Palma de Mallorca, Spain. ELRA Language Resource Association.
Cite (Informal):
EL-MIA: Quantifying Membership Inference Risks of Sensitive Entities in LLMs (Satvaty et al., LREC 2026)
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