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Cyberthreats are a permanent concern in our modern technological world. In the recent years, sophisticated traffic analysis techniques and anomaly detection (AD) algorithms have been employed to face the more and more subversive adversarial…

Machine Learning · Computer Science 2022-05-17 Paul Irofti , Andrei Pătraşcu , Andrei Iulian Hîji

Graph anomaly detection aims to identify abnormal patterns in networks, but faces significant challenges from label scarcity and extreme class imbalance. While graph contrastive learning offers a promising unsupervised solution, existing…

Machine Learning · Computer Science 2026-01-30 Kamal Berahmand , Saman Forouzandeh , Mehrnoush Mohammadi , Parham Moradi , Mahdi Jalili

Graph Convolutional Network (GCN) are widely used in Graph Anomaly Detection (GAD) due to their natural compatibility with graph structures, resulting in significant performance improvements. However, most researchers approach GAD as a…

Machine Learning · Computer Science 2024-11-05 Shelei Li , Yong Chai Tan , Tai Vincent

With the widespread availability of sensor data across industrial and operational systems, we frequently encounter heterogeneous time series from multiple systems. Anomaly detection is crucial for such systems to facilitate predictive…

Machine Learning · Computer Science 2025-04-22 Sarah Alnegheimish , Zelin He , Matthew Reimherr , Akash Chandrayan , Abhinav Pradhan , Luca D'Angelo

Graph anomaly detection (GAD) aims to identify nodes from a graph that are significantly different from normal patterns. Most previous studies are model-driven, focusing on enhancing the detection effect by improving the model structure.…

Machine Learning · Computer Science 2025-01-27 Yitong Hao , Enbo He , Yue Zhang , Guisheng Yin

Responding to the challenge of detecting unusual radar targets in a well identified environment, innovative anomaly and novelty detection methods keep emerging in the literature. This work aims at presenting a benchmark gathering common and…

Signal Processing · Electrical Eng. & Systems 2021-06-22 Martin Bauw , Santiago Velasco-Forero , Jesus Angulo , Claude Adnet , Olivier Airiau

In anomaly detection (AD), one seeks to identify whether a test sample is abnormal, given a data set of normal samples. A recent and promising approach to AD relies on deep generative models, such as variational autoencoders (VAEs), for…

Machine Learning · Computer Science 2021-11-05 Tal Daniel , Thanard Kurutach , Aviv Tamar

Existing unsupervised distillation-based methods rely on the differences between encoded and decoded features to locate abnormal regions in test images. However, the decoder trained only on normal samples still reconstructs abnormal patch…

Computer Vision and Pattern Recognition · Computer Science 2025-01-03 Xiaolei Wang , Xiaoyang Wang , Huihui Bai , Eng Gee Lim , Jimin Xiao

Graph anomaly detection (GAD) has garnered increasing attention in recent years, yet remains challenging due to two key factors: (1) label scarcity stemming from the high cost of annotations and (2) homophily disparity at node and class…

Machine Learning · Computer Science 2026-01-30 Yunhui Liu , Jiashun Cheng , Yiqing Lin , Qizhuo Xie , Jia Li , Fugee Tsung , Hongzhi Yin , Tao Zheng , Jianhua Zhao , Tieke He

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

Graph autoencoders (GAEs) are powerful tools in representation learning for graph embedding. However, the performance of GAEs is very dependent on the quality of the graph structure, i.e., of the adjacency matrix. In other words, GAEs would…

Machine Learning · Computer Science 2021-03-24 Rui Zhang , Yunxing Zhang , Xuelong Li

Unsupervised anomaly detection (UAD) from images strives to model normal data distributions, creating discriminative representations to distinguish and precisely localize anomalies. Despite recent advancements in the efficient and unified…

Computer Vision and Pattern Recognition · Computer Science 2025-03-11 Wenxin Ma , Qingsong Yao , Xiang Zhang , Zhelong Huang , Zihang Jiang , S. Kevin Zhou

Video anomaly detection (VAD) is a challenging task that detects anomalous frames in continuous surveillance videos. Most previous work utilizes the spatio-temporal correlation of visual features to distinguish whether there are…

Computer Vision and Pattern Recognition · Computer Science 2025-12-16 Guangyu Dai , Dong Chen , Siliang Tang , Yueting Zhuang

T2 hyperintensities in spinal cord MR images are crucial biomarkers for conditions such as degenerative cervical myelopathy. However, current clinical diagnoses primarily rely on manual evaluation. Deep learning methods have shown promise…

Image and Video Processing · Electrical Eng. & Systems 2025-03-18 Qi Zhang , Xiuyuan Chen , Ziyi He , Kun Wang , Lianming Wu , Hongxing Shen , Jianqi Sun

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

Anomaly detection in smart power grids is a critical challenge due to the complexity, heterogeneity, and dynamic nature of sensor data streams. Existing one-class classification methods, particularly Subspace Support Vector Data Description…

Machine Learning · Computer Science 2026-04-24 Thomas Debelle , Fahad Sohrab , Pekka Abrahamsson , Moncef Gabbouj

Image-based inspection systems have been widely deployed in manufacturing production lines. Due to the scarcity of defective samples, unsupervised anomaly detection that only leverages normal samples during training to detect various…

Image and Video Processing · Electrical Eng. & Systems 2024-11-22 Chengyu Tao , Hao Xu , Juan Du

Unlike conventional anomaly detection research that focuses on point anomalies, our goal is to detect anomalous collections of individual data points. In particular, we perform group anomaly detection (GAD) with an emphasis on irregular…

Computer Vision and Pattern Recognition · Computer Science 2018-04-16 Raghavendra Chalapathy , Edward Toth , Sanjay Chawla

Anomaly detection (AD) is the identification of data samples that do not fit a learned data distribution. As such, AD systems can help physicians to determine the presence, severity, and extension of a pathology. Deep generative models,…

Image and Video Processing · Electrical Eng. & Systems 2021-04-12 Jaime Simarro , Ezequiel de la Rosa , Thijs Vande Vyvere , David Robben , Diana M. Sima

This paper studies the problem of detecting anomalous graphs using a machine learning model trained on only normal graphs, which has many applications in molecule, biology, and social network data analysis. We present a self-discriminative…

Machine Learning · Computer Science 2023-10-11 Jinyu Cai , Yunhe Zhang , Jicong Fan