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The core challenge in unsupervised anomaly detection is identifying abnormal patterns without prior knowledge of their characteristics. While existing methods have addressed aspects of this problem, they often struggle to learn a robust…

Machine Learning · Computer Science 2026-05-12 Prithul Sarker , Sushmita Sarker , Nicholas G. Murray , Alireza Tavakkoli

Generative models, such as Generative Adversarial Networks (GANs), have been used for unsupervised anomaly detection. While performance keeps improving, several limitations exist particularly attributed to difficulties at capturing…

Machine Learning · Computer Science 2022-02-03 Nikolaos Dionelis , Mehrdad Yaghoobi , Sotirios A. Tsaftaris

Time series anomaly detection (TSAD) has long been a hot research topic in data mining due to its various applications. Recent studies challenge the effectiveness of popular deep learning methods for TSAD, suggesting their failure in…

Machine Learning · Computer Science 2026-05-29 Qideng Tang , Dai Chaofan , Wubin Ma , Yahui Wu , Haohao Zhou , Tao Zhang , Huan Li , Dalin Zhang

Time series anomaly detection plays a crucial role in a wide range of real-world applications. Given that time series data can exhibit different patterns at different sampling granularities, multi-scale modeling has proven beneficial for…

Machine Learning · Computer Science 2025-10-15 Beibu Li , Qichao Shentu , Yang Shu , Hui Zhang , Ming Li , Ning Jin , Bin Yang , Chenjuan Guo

In practice, machine learning methods commonly require anomaly detection (AD) to filter inputs or detect distributional shifts. Typically, this is implemented by running a separate AD model alongside the primary model. However, this…

Machine Learning · Computer Science 2026-03-19 Luca Hinkamp , Simon Klüttermann , Emmanuel Müller

Recently, anomaly scores have been formulated using reconstruction loss of the adversarially learned generators and/or classification loss of discriminators. Unavailability of anomaly examples in the training data makes optimization of such…

Computer Vision and Pattern Recognition · Computer Science 2024-10-28 Muhammad Zaigham Zaheer , Jin Ha Lee , Arif Mahmood , Marcella Astrid , Seung-Ik Lee

Time series anomaly detection is extensively studied in statistics, economics, and computer science. Over the years, numerous methods have been proposed for time series anomaly detection using deep learning-based methods. Many of these…

Machine Learning · Computer Science 2022-08-25 Shahroz Tariq , Binh M. Le , Simon S. Woo

In the domain of anomaly detection, methods often excel in either high-level semantic or low-level industrial benchmarks, rarely achieving cross-domain proficiency. Semantic anomalies are novelties that differ in meaning from the training…

Computer Vision and Pattern Recognition · Computer Science 2024-07-18 Luc P. J. Sträter , Mohammadreza Salehi , Efstratios Gavves , Cees G. M. Snoek , Yuki M. Asano

Detecting structural instability and anomalies in high-dimensional financial time series is challenging due to complex temporal dependence and evolving cross-sectional structure. We propose ReGEN-TAD, an interpretable generative framework…

Machine Learning · Statistics 2026-03-10 Waldyn G Martinez

Traditional reconstruction-based methods have struggled to achieve competitive performance in anomaly detection. In this paper, we introduce Denoising Diffusion Anomaly Detection (DDAD), a novel denoising process for image reconstruction…

Computer Vision and Pattern Recognition · Computer Science 2025-04-29 Arian Mousakhan , Thomas Brox , Jawad Tayyub

Generative adversarial networks (GANs) have shown promise for various problems including anomaly detection. When anomaly detection is performed using GAN models that learn only the features of normal data samples, data that are not similar…

Machine Learning · Computer Science 2020-12-23 Teguh Budianto , Tomohiro Nakai , Kazunori Imoto , Takahiro Takimoto , Kosuke Haruki

Semi-supervised and unsupervised Generative Adversarial Networks (GAN)-based methods have been gaining popularity in anomaly detection task recently. However, GAN training is somewhat challenging and unstable. Inspired from previous work in…

Computer Vision and Pattern Recognition · Computer Science 2019-02-20 Ha Son Vu , Daisuke Ueta , Kiyoshi Hashimoto , Kazuki Maeno , Sugiri Pranata , Sheng Mei Shen

Anomaly detection holds considerable industrial significance, especially in scenarios with limited anomalous data. Currently, reconstruction-based and unsupervised representation-based approaches are the primary focus. However, unsupervised…

Computer Vision and Pattern Recognition · Computer Science 2025-12-29 Xiao Jin , Liang Diao , Qixin Xiao , Yifan Hu , Ziqi Zhang , Yuchen Liu , Haisong Gu

Current Generative Adversarial Network (GAN)-based approaches for time series generation face challenges such as suboptimal convergence, information loss in embedding spaces, and instability. To overcome these challenges, we introduce an…

Machine Learning · Computer Science 2024-10-29 MohammadReza EskandariNasab , Shah Muhammad Hamdi , Soukaina Filali Boubrahimi

There is growing interest in applying graph-based methods to Time Series Anomaly Detection (TSAD), particularly Graph Neural Networks (GNNs), as they naturally model dependencies among multivariate signals. GNNs are typically used as…

Machine Learning · Computer Science 2026-03-11 Federico Bello , Gonzalo Chiarlone , Marcelo Fiori , Gastón García González , Federico Larroca

Anomaly detection from graph data has drawn much attention due to its practical significance in many critical applications including cybersecurity, finance, and social networks. Existing data mining and machine learning methods are either…

Machine Learning · Computer Science 2022-01-25 Yu Zheng , Ming Jin , Yixin Liu , Lianhua Chi , Khoa T. Phan , Yi-Ping Phoebe Chen

While GNN-based detection methods excel at identifying overt outliers, they often struggle with boundary anomalies -- subtly camouflaged nodes that are difficult to distinguish from normal instances. This limitation highlights a fundamental…

Machine Learning · Computer Science 2026-03-05 Hwan Kim , Junghoon Kim , Sungsu Lim

As a kind of generative self-supervised learning methods, generative adversarial nets have been widely studied in the field of anomaly detection. However, the representation learning ability of the generator is limited since it pays too…

Computer Vision and Pattern Recognition · Computer Science 2021-07-28 Xuan Xia , Xizhou Pan , Xing He , Jingfei Zhang , Ning Ding , Lin Ma

Deep generative models for anomaly detection in multivariate time-series are typically trained by maximizing data likelihood. However, likelihood in observation space measures marginal density rather than conformity to structured temporal…

Artificial Intelligence · Computer Science 2026-03-13 David Baumgartner , Eliezer de Souza da Silva , Iñigo Urteaga

Time series anomaly detection plays a vital role in a wide range of applications. Existing methods require training one specific model for each dataset, which exhibits limited generalization capability across different target datasets,…

Machine Learning · Computer Science 2025-03-04 Qichao Shentu , Beibu Li , Kai Zhao , Yang Shu , Zhongwen Rao , Lujia Pan , Bin Yang , Chenjuan Guo