Fight Poison with Poison: Enhancing Robustness in Few-shot Machine-Generated Text Detection with Adversarial Training

Wenjing Duan, Qi Zhou, Yuanfan Li


Abstract
Machine-generated text (MGT) detection is critical for regulating online information ecosystems, yet existing detectors often fail under limited fresh supervision and humanization-oriented attacks. We study this problem as few-shot robustness recovery under evolving generators, domains, and attack patterns, and use threat modeling to diagnose detector failures from an attacker’s viewpoint. We identify unstable local boundary estimation as a key failure mode: under scarce supervision, humanized MGT can induce prediction flips, logit drift, and clean–adversarial representation misalignment. To address this issue, we propose RAG-GuidEd Attacker Strengthens ConTrastive Few-shot Detector (REACT), a threat-aware few-shot robustness framework. REACT uses a dynamic retrieval-guided attacker to generate boundary-oriented humanized rewrites from extreme positive–negative anchors, and trains the detector with a pairwise boundary contrastive objective to stabilize clean–adversarial local geometry. Alternating attacker–detector updates further form a co-evolutionary curriculum. Experiments on 4 datasets with 4 shot sizes and 3 random seeds show that REACT improves average detection F1 by 4.95 points over 8 SOTA detectors and reduces average attack success rate under 4 strong attacks by 3.66 percentage points.
Anthology ID:
2026.emnlp-main.171
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3921–3947
Language:
URL:
https://aclanthology.org/2026.emnlp-main.171/
DOI:
Bibkey:
Cite (ACL):
Wenjing Duan, Qi Zhou, and Yuanfan Li. 2026. Fight Poison with Poison: Enhancing Robustness in Few-shot Machine-Generated Text Detection with Adversarial Training. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 3921–3947, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Fight Poison with Poison: Enhancing Robustness in Few-shot Machine-Generated Text Detection with Adversarial Training (Duan et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.171.pdf