Win-k: Improved Membership Inference Attacks on Small Language Models

Fuente: arXiv
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Main Authors: Arkhmammadova, Roya, Tamar, Hosein Madadi, Gursoy, M. Emre
Format: Preprint
Published: 2025
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author Arkhmammadova, Roya
Tamar, Hosein Madadi
Gursoy, M. Emre
author_facet Arkhmammadova, Roya
Tamar, Hosein Madadi
Gursoy, M. Emre
contents Small language models (SLMs) are increasingly valued for their efficiency and deployability in resource-constrained environments, making them useful for on-device, privacy-sensitive, and edge computing applications. On the other hand, membership inference attacks (MIAs), which aim to determine whether a given sample was used in a model's training, are an important threat with serious privacy and intellectual property implications. In this paper, we study MIAs on SLMs. Although MIAs were shown to be effective on large language models (LLMs), they are relatively less studied on emerging SLMs, and furthermore, their effectiveness decreases as models get smaller. Motivated by this finding, we propose a new MIA called win-k, which builds on top of a state-of-the-art attack (min-k). We experimentally evaluate win-k by comparing it with five existing MIAs using three datasets and eight SLMs. Results show that win-k outperforms existing MIAs in terms of AUROC, TPR @ 1% FPR, and FPR @ 99% TPR metrics, especially on smaller models.
format Preprint
id arxiv_https___arxiv_org_abs_2508_01268
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Win-k: Improved Membership Inference Attacks on Small Language Models
Arkhmammadova, Roya
Tamar, Hosein Madadi
Gursoy, M. Emre
Artificial Intelligence
Cryptography and Security
Small language models (SLMs) are increasingly valued for their efficiency and deployability in resource-constrained environments, making them useful for on-device, privacy-sensitive, and edge computing applications. On the other hand, membership inference attacks (MIAs), which aim to determine whether a given sample was used in a model's training, are an important threat with serious privacy and intellectual property implications. In this paper, we study MIAs on SLMs. Although MIAs were shown to be effective on large language models (LLMs), they are relatively less studied on emerging SLMs, and furthermore, their effectiveness decreases as models get smaller. Motivated by this finding, we propose a new MIA called win-k, which builds on top of a state-of-the-art attack (min-k). We experimentally evaluate win-k by comparing it with five existing MIAs using three datasets and eight SLMs. Results show that win-k outperforms existing MIAs in terms of AUROC, TPR @ 1% FPR, and FPR @ 99% TPR metrics, especially on smaller models.
title Win-k: Improved Membership Inference Attacks on Small Language Models
topic Artificial Intelligence
Cryptography and Security
url https://arxiv.org/abs/2508.01268