arXiv Machine Learning

NormDetect: Anchored Calibration for Low-False-Positive Detection of Machine-Generated Web Text

NormDetect is a new detection method that anchors a learned per-section head to a normalized zero-shot score to improve low‑false‑positive detection of machine‑generated web text. By blending the two scores with a weight chosen on training folds under a human false‑positive rate cap, it raises recall by 5.0 points over normalized Binoculars at a calibrated 0.1% FPR on the RAID benchmark. The method maintains a human FPR bound of at most 1% in every section, outperforming other detectors within this bound.

arXiv AI
Oct 27

Local Entropy Fluctuations for Black-Box LLM-Generated Text Detection

The paper introduces a new metric, Relative Peak Prominence Rate (RelPPR), to detect black-box LLM-generated text by measuring localized entropy fluctuations. It shows that existing dual-model and resampling-based detectors fail on instruction-conditioned text, and that RelPPR outperforms them across diverse models and datasets. The authors provide code for their detector on GitHub.

By Xinpeng Wang, Bruce Rushing, Zhizhen Chen, Zhe Zeng
arXiv Computation and Language
Oct 12

Measuring Artifact Reliance in Machine-Generated Text Detectors

The study evaluates machine‑generated text detectors on scientific literature, finding that many detectors perform near perfectly on certain benchmarks due to superficial formatting cues rather than genuine linguistic differences. A logistic regression using 27 superficial features achieved macro‑F1 scores between 0.833 and 0.997, outperforming other detectors on arXiv subsets. The most powerful cue was the PDF extraction artifact—human texts preserve line breaks while generated texts appear as a single block—allowing classification at 0.996 AUC. By introducing format counterfactuals and normalizing formatting, the authors demonstrate that re‑wrapping machine‑written abstracts can flip 20–27% of detector decisions, reducing the generalization gap and improving out‑of‑domain performance.

By Anastasia Voznyuk, Andrey Grabovoy
arXiv AI
Jun 10

Attacks on Machine-Text Detectors Retain Stylistic Fingerprints

arXiv:2505. 14608v3 Announce Type: replace-cross Abstract: Despite considerable progress in the development of machine-text detectors, the ease with which machine-text can be manipulated to evade detection has led to suggestions that the problem is inherently intractable.

By Rafael Rivera Soto, Barry Chen, Nicholas Andrews
arXiv Machine Learning
Sep 25

Robust Detection of LLM-Generated Text under Contamination

The paper investigates how to detect text generated by large language models (LLMs) when the data has been edited or contaminated. By modeling human and machine text as finite-order Markov processes with Huber contamination, the authors derive an exact boundary that determines when reliable detection is possible. They show that a clipped likelihood-ratio test can achieve vanishing worst‑case errors below this boundary and that clipping improves robustness across several detectors and datasets, yielding significant gains in true‑positive rates at a fixed false‑positive rate.

By Jiaxun Li, Saptarshi Chakraborty, Ambuj Tewari
arXiv AI
Oct 31

TextSeal2: Distortion-Free LLM Watermarking with Copula Mixing and Memoryless Races

TextSeal2 is a distortion‑free watermarking method for large language models that maintains signal integrity during speculative decoding. It merges multiple keys into a single virtual key using a Gaussian copula, ensuring that the acceptance rate and output diversity remain unchanged while adding no measurable inference latency. Experiments on three LLMs show that TextSeal2 detects 8–22 percentage points more 100‑token answers than its predecessor TextSeal and outperforms textGrain under speculative decoding, all without post‑logits optimization.

By Tom Sander, Pierre Fernandez, Itai Gat, Haiming Bao, Jiaxin Shi, Jason Park, Valeriu Lacatusu, Sylvestre-Alvise Rebuffi, Hongyan Chang, Hady Elsahar, Tom\'{a}\v{s} Sou\v{c}ek, Tuan Tran, Surya Parimi, Alexandre Mourachko