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Anomaly detection seeks to identify unusual phenomena, a central task in science and industry. The task is inherently unsupervised as anomalies are unexpected and unknown during training. Recent advances in self-supervised representation…

Machine Learning · Computer Science 2022-10-20 Tal Reiss , Niv Cohen , Eliahu Horwitz , Ron Abutbul , Yedid Hoshen

Several techniques for multivariate time series anomaly detection have been proposed recently, but a systematic comparison on a common set of datasets and metrics is lacking. This paper presents a systematic and comprehensive evaluation of…

Machine Learning · Computer Science 2021-09-24 Astha Garg , Wenyu Zhang , Jules Samaran , Savitha Ramasamy , Chuan-Sheng Foo

Most of the existing methods for anomaly detection use only positive data to learn the data distribution, thus they usually need a pre-defined threshold at the detection stage to determine whether a test instance is an outlier.…

Machine Learning · Computer Science 2019-03-19 Kai Tian , Shuigeng Zhou , Jianping Fan , Jihong Guan

Anomaly detection is a classical problem in computer vision, namely the determination of the normal from the abnormal when datasets are highly biased towards one class (normal) due to the insufficient sample size of the other class…

Computer Vision and Pattern Recognition · Computer Science 2018-11-14 Samet Akcay , Amir Atapour-Abarghouei , Toby P. Breckon

A method for unsupervised contextual anomaly detection is proposed using a cross-linked pair of Variational Auto-Encoders for assigning a normality score to an observation. The method enables a distinct separation of contextual from…

Machine Learning · Statistics 2019-04-02 Yaniv Shulman

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

We introduce a powerful student-teacher framework for the challenging problem of unsupervised anomaly detection and pixel-precise anomaly segmentation in high-resolution images. Student networks are trained to regress the output of a…

Computer Vision and Pattern Recognition · Computer Science 2020-09-08 Paul Bergmann , Michael Fauser , David Sattlegger , Carsten Steger

Anomaly detection is the task of identifying abnormal behavior of a system. Anomaly detection in computational workflows is of special interest because of its wide implications in various domains such as cybersecurity, finance, and social…

Machine Learning · Computer Science 2023-10-03 Hongwei Jin , Krishnan Raghavan , George Papadimitriou , Cong Wang , Anirban Mandal , Ewa Deelman , Prasanna Balaprakash

Automated anomaly detection is essential for managing information and communications technology (ICT) systems to maintain reliable services with minimum burden on operators. For detecting varying and continually emerging anomalies as…

Machine Learning · Statistics 2018-12-19 Yasuhiro Ikeda , Keisuke Ishibashi , Yuusuke Nakano , Keishiro Watanabe , Ryoichi Kawahara

Dynamic graph anomaly detection (DGAD) is critical for many real-world applications but remains challenging due to the scarcity of labeled anomalies. Existing methods are either unsupervised or semi-supervised: unsupervised methods avoid…

Machine Learning · Computer Science 2026-02-24 Yuxing Tian , Yiyan Qi , Fengran Mo , Weixu Zhang , Jian Guo , Jian-Yun Nie

Accurate and automated detection of anomalous samples in a natural image dataset can be accomplished with a probabilistic model for end-to-end modeling of images. Such images have heterogeneous complexity, however, and a probabilistic model…

Machine Learning · Computer Science 2018-09-05 Takashi Matsubara , Kenta Hama , Ryosuke Tachibana , Kuniaki Uehara

Recently, the introduction of the generative adversarial network (GAN) and its variants has enabled the generation of realistic synthetic samples, which has been used for enlarging training sets. Previous work primarily focused on data…

Machine Learning · Computer Science 2018-08-27 Swee Kiat Lim , Yi Loo , Ngoc-Trung Tran , Ngai-Man Cheung , Gemma Roig , Yuval Elovici

Graph anomaly detection (GAD) has attracted growing interest for its crucial ability to uncover irregular patterns in broad applications. Semi-supervised GAD, which assumes a subset of annotated normal nodes available during training, is…

Machine Learning · Computer Science 2026-02-03 Guolei Zeng , Hezhe Qiao , Guoguo Ai , Jinsong Guo , Guansong Pang

Generative models based on variational autoencoders are a popular technique for detecting anomalies in images in a semi-supervised context. A common approach employs the anomaly score to detect the presence of anomalies, and it is known to…

Machine Learning · Computer Science 2024-07-30 Muhammad Rashid , Elvio Amparore , Enrico Ferrari , Damiano Verda

Self-supervised learning (SSL) is a growing torrent that has recently transformed machine learning and its many real world applications, by learning on massive amounts of unlabeled data via self-generated supervisory signals. Unsupervised…

Machine Learning · Computer Science 2023-08-29 Leman Akoglu , Jaemin Yoo

Unsupervised anomaly detection is a challenging task. Autoencoders (AEs) or generative models are often employed to model the data distribution of normal inputs and subsequently identify anomalous, out-of-distribution inputs by high…

Machine Learning · Computer Science 2025-06-12 Yalin Liao , Austin J. Brockmeier

Unsupervised anomaly detection is a challenging task in industrial applications since it is impracticable to collect sufficient anomalous samples. In this paper, a novel Self-Supervised Guided Segmentation Framework (SGSF) is proposed by…

Computer Vision and Pattern Recognition · Computer Science 2022-09-27 Peng Xing , Yanpeng Sun , Zechao Li

Anomaly detection has wide applications in machine intelligence but is still a difficult unsolved problem. Major challenges include the rarity of labeled anomalies and it is a class highly imbalanced problem. Traditional unsupervised…

Machine Learning · Computer Science 2021-04-27 Zhi Chen , Jiang Duan , Li Kang , Guoping Qiu

We propose the Autoencoding Binary Classifiers (ABC), a novel supervised anomaly detector based on the Autoencoder (AE). There are two main approaches in anomaly detection: supervised and unsupervised. The supervised approach accurately…

Machine Learning · Statistics 2019-03-27 Yuki Yamanaka , Tomoharu Iwata , Hiroshi Takahashi , Masanori Yamada , Sekitoshi Kanai

Anomaly detection has been considered under several extents of prior knowledge. Unsupervised methods do not require any labelled data, whereas semi-supervised methods leverage some known anomalies. Inspired by mixture-of-experts models and…

Machine Learning · Computer Science 2022-10-14 J. -P. Schulze , P. Sperl , K. Böttinger