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Unsupervised anomaly detection stands as an important problem in machine learning, with applications in financial fraud prevention, network security and medical diagnostics. Existing unsupervised anomaly detection algorithms rarely perform…

Machine Learning · Computer Science 2026-02-04 Pritam Kar , Rahul Bordoloi , Olaf Wolkenhauer , Saptarshi Bej

Anomaly detection is crucial for understanding unusual behaviors in data, as anomalies offer valuable insights. This paper introduces Dependency-based Anomaly Detection (DepAD), a general framework that utilizes variable dependencies to…

Machine Learning · Computer Science 2024-04-18 Sha Lu , Lin Liu , Kui Yu , Thuc Duy Le , Jixue Liu , Jiuyong Li

Anomaly detection is to recognize samples that differ in some respect from the training observations. These samples which do not conform to the distribution of normal data are called outliers or anomalies. In real-world anomaly detection…

Computer Vision and Pattern Recognition · Computer Science 2022-07-05 Vahid Reza Khazaie , Anthony Wong , Yalda Mohsenzadeh

To improve the identification of potential anomaly patterns in complex user behavior, this paper proposes an anomaly detection method based on a deep mixture density network. The method constructs a Gaussian mixture model parameterized by a…

Machine Learning · Computer Science 2025-05-20 Lu Dai , Wenxuan Zhu , Xuehui Quan , Renzi Meng , Sheng Chai , Yichen Wang

Timely detection of abrupt anomalies is crucial for real-time monitoring and security of modern systems producing high-dimensional data. With this goal, we propose effective and scalable algorithms. Proposed algorithms are nonparametric as…

Machine Learning · Computer Science 2020-02-19 Mehmet Necip Kurt , Yasin Yilmaz , Xiaodong Wang

Anomaly detection is facing with emerging challenges in many important industry domains, such as cyber security and online recommendation and advertising. The recent trend in these areas calls for anomaly detection on time-evolving data…

Machine Learning · Computer Science 2019-07-16 Zheng Gao , Lin Guo , Chi Ma , Xiao Ma , Kai Sun , Hang Xiang , Xiaoqiang Zhu , Hongsong Li , Xiaozhong Liu

Hybrid methods have been shown to outperform pure statistical and pure deep learning methods at both forecasting tasks, and at quantifying the uncertainty associated with those forecasts (prediction intervals). One example is Multivariate…

Machine Learning · Computer Science 2022-02-28 Thabang Mathonsi , Terence L van Zyl

We propose a method that performs anomaly detection and localisation within heterogeneous data using a pairwise undirected mixed graphical model. The data are a mixture of categorical and quantitative variables, and the model is learned…

Machine Learning · Statistics 2016-07-21 Romain Laby , François Roueff , Alexandre Gramfort

Anomaly detection aims to identify samples that deviate from the nominal data distribution and is central to many safety-critical applications. However, developing effective anomaly detection methods for categorical, mixed-type, and…

Machine Learning · Computer Science 2026-05-29 Lixing Zhang , Yuchen Liang , Liyan Xie

Though anomaly detection (AD) can be viewed as a classification problem (nominal vs. anomalous) it is usually treated in an unsupervised manner since one typically does not have access to, or it is infeasible to utilize, a dataset that…

Machine Learning · Computer Science 2023-01-30 Lukas Ruff , Robert A. Vandermeulen , Billy Joe Franks , Klaus-Robert Müller , Marius Kloft

Detecting anomalies in large complex systems is a critical and challenging task. The difficulties arise from several aspects. First, collecting ground truth labels or prior knowledge for anomalies is hard in real-world systems, which often…

Machine Learning · Computer Science 2021-06-01 Huiling Qin , Xianyuan Zhan , Yu Zheng

Anomaly detection (AD) is a critical task across domains such as cybersecurity and healthcare. In the unsupervised setting, an effective and theoretically-grounded principle is to train classifiers to distinguish normal data from…

Machine Learning · Statistics 2025-06-18 Matthew Lau , Tian-Yi Zhou , Xiangchi Yuan , Jizhou Chen , Wenke Lee , Xiaoming Huo

With a growing number of robots being deployed across diverse applications, robust multimodal anomaly detection becomes increasingly important. In robotic manipulation, failures typically arise from (1) robot-driven anomalies due to an…

Robotics · Computer Science 2025-06-25 Christoph Willibald , Daniel Sliwowski , Dongheui Lee

It is widely recognized that deep neural networks are sensitive to bias in the data. This means that during training these models are likely to learn spurious correlations between data and labels, resulting in limited generalization…

Machine Learning · Computer Science 2024-12-06 Vito Paolo Pastore , Massimiliano Ciranni , Davide Marinelli , Francesca Odone , Vittorio Murino

Reconstruction-based anomaly detection models achieve their purpose by suppressing the generalization ability for anomaly. However, diverse normal patterns are consequently not well reconstructed as well. Although some efforts have been…

Computer Vision and Pattern Recognition · Computer Science 2023-03-10 Wenrui Liu , Hong Chang , Bingpeng Ma , Shiguang Shan , Xilin Chen

In recent years, there has been a growing interest in identifying anomalous structure within multivariate data streams. We consider the problem of detecting collective anomalies, corresponding to intervals where one or more of the data…

Methodology · Statistics 2019-09-05 Alexander T M Fisch , Idris A Eckley , Paul Fearnhead

Anomaly Detection in multivariate time series is a major problem in many fields. Due to their nature, anomalies sparsely occur in real data, thus making the task of anomaly detection a challenging problem for classification algorithms to…

Machine Learning · Computer Science 2023-08-08 Anastasios Iliopoulos , John Violos , Christos Diou , Iraklis Varlamis

Reconstruction-based methods have been commonly used for unsupervised anomaly detection, in which a normal image is reconstructed and compared with the given test image to detect and locate anomalies. Recently, diffusion models have shown…

Computer Vision and Pattern Recognition · Computer Science 2024-04-30 Di Wu , Shicai Fan , Xue Zhou , Li Yu , Yuzhong Deng , Jianxiao Zou , Baihong Lin

Reconstruction-based approaches have achieved remarkable outcomes in anomaly detection. The exceptional image reconstruction capabilities of recently popular diffusion models have sparked research efforts to utilize them for enhanced…

Computer Vision and Pattern Recognition · Computer Science 2023-12-12 Haoyang He , Jiangning Zhang , Hongxu Chen , Xuhai Chen , Zhishan Li , Xu Chen , Yabiao Wang , Chengjie Wang , Lei Xie

Anomalies represent deviations from the intended system operation and can lead to decreased efficiency as well as partial or complete system failure. As the causes of anomalies are often unknown due to complex system dynamics, efficient…

Machine Learning · Computer Science 2021-08-31 Benjamin Lindemann , Benjamin Maschler , Nada Sahlab , Michael Weyrich