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Graph anomaly detection (GAD) aims to identify nodes or substructures whose behavior or attributes deviate significantly from the overall pattern in graph-structured data, with critical applications in financial risk control, social network…

Machine Learning · Computer Science 2026-05-27 Yuxin Yang , Limei Hu , Feng Chen

Despite graph neural networks' (GNNs) great success in modelling graph-structured data, out-of-distribution (OOD) test instances still pose a great challenge for current GNNs. One of the most effective techniques to detect OOD nodes is to…

Machine Learning · Computer Science 2025-04-11 Danny Wang , Ruihong Qiu , Guangdong Bai , Zi Huang

Network (or graph) embedding is the task to map the nodes of a graph to a lower dimensional vector space, such that it preserves the graph properties and facilitates the downstream network mining tasks. Real world networks often come with…

Social and Information Networks · Computer Science 2020-07-21 Sambaran Bandyopadhyay , Saley Vishal Vivek , M. N. Murty

Unsupervised graph anomaly detection aims at identifying rare patterns that deviate from the majority in a graph without the aid of labels, which is important for a variety of real-world applications. Recent advances have utilized Graph…

Machine Learning · Computer Science 2025-05-27 Yuanchen Bei , Sheng Zhou , Jinke Shi , Yao Ma , Haishuai Wang , Jiajun Bu

Graph neural networks (GNNs) are proven effective in extracting complex node and structural information from graph data. While current GNNs perform well in node classification tasks within in-distribution (ID) settings, real-world scenarios…

Machine Learning · Computer Science 2025-05-08 Tao Yin , Chen Zhao , Xiaoyan Liu , Minglai Shao

Outlier detection is an important topic in machine learning and has been used in a wide range of applications. Outliers are objects that are few in number and deviate from the majority of objects. As a result of these two properties, we…

Machine Learning · Computer Science 2022-04-22 Xusheng Du , Enguang Zuo , Zhenzhen He , Jiong Yu

Graph anomaly detection (GAD) is a vital task in graph-based machine learning and has been widely applied in many real-world applications. The primary goal of GAD is to capture anomalous nodes from graph datasets, which evidently deviate…

Machine Learning · Computer Science 2022-12-05 Jingcan Duan , Siwei Wang , Pei Zhang , En Zhu , Jingtao Hu , Hu Jin , Yue Liu , Zhibin Dong

Detecting out-of-distribution (OOD) graphs is crucial for ensuring the safety and reliability of Graph Neural Networks. In unsupervised graph-level OOD detection, models are typically trained using only in-distribution (ID) data, resulting…

Machine Learning · Computer Science 2026-03-03 Li Sun , Lanxu Yang , Jiayu Tian , Bowen Fang , Xiaoyan Yu , Junda Ye , Peng Tang , Hao Peng , Philip S. Yu

Graph Anomaly Detection (GAD) aims to identify nodes that deviate from the majority within a graph, playing a crucial role in applications such as social networks and e-commerce. Despite the current advancements in deep learning-based GAD,…

Machine Learning · Computer Science 2025-08-20 Yunfeng Zhao , Yixin Liu , Shiyuan Li , Qingfeng Chen , Yu Zheng , Shirui Pan

Graph machine learning has witnessed rapid growth, driving advancements across diverse domains. However, the in-distribution assumption, where training and testing data share the same distribution, often breaks in real-world scenarios,…

Machine Learning · Computer Science 2025-02-13 Tingyi Cai , Yunliang Jiang , Yixin Liu , Ming Li , Changqin Huang , Shirui Pan

Graph anomaly detection aims to identify unusual patterns in graph-based data, with wide applications in fields such as web security and financial fraud detection. Existing methods typically rely on contrastive learning, assuming that a…

Machine Learning · Computer Science 2025-05-26 Di Jin , Jingyi Cao , Xiaobao Wang , Bingdao Feng , Dongxiao He , Longbiao Wang , Jianwu Dang

Out-of-distribution (OOD) generalization has gained increasing attentions for learning on graphs, as graph neural networks (GNNs) often exhibit performance degradation with distribution shifts. The challenge is that distribution shifts on…

Machine Learning · Computer Science 2024-08-19 Qitian Wu , Fan Nie , Chenxiao Yang , Tianyi Bao , Junchi Yan

Graph out-of-distribution (OOD) generalization remains a major challenge in graph learning since graph neural networks (GNNs) often suffer from severe performance degradation under distribution shifts. Invariant learning, aiming to extract…

Machine Learning · Computer Science 2025-02-14 Wenyu Mao , Jiancan Wu , Haoyang Liu , Yongduo Sui , Xiang Wang

Graph anomaly detection (GAD) has achieved success and has been widely applied in various domains, such as fraud detection, cybersecurity, finance security, and biochemistry. However, existing graph anomaly detection algorithms focus on…

Machine Learning · Computer Science 2023-08-03 Xing Ai , Jialong Zhou , Yulin Zhu , Gaolei Li , Tomasz P. Michalak , Xiapu Luo , Kai Zhou

A fundamental challenge confronting supervised graph outlier detection algorithms is the prevalent problem of class imbalance, where the scarcity of outlier instances compared to normal instances often results in suboptimal performance.…

Machine Learning · Computer Science 2024-11-26 Kay Liu , Hengrui Zhang , Ziqing Hu , Fangxin Wang , Philip S. Yu

Traditional machine learning methods heavily rely on the independent and identically distribution assumption, which imposes limitations when the test distribution deviates from the training distribution. To address this crucial issue,…

Machine Learning · Computer Science 2024-03-26 Qin Tian , Wenjun Wang , Chen Zhao , Minglai Shao , Wang Zhang , Dong Li

Unsupervised graph-level anomaly detection (UGAD) has attracted increasing interest due to its widespread application. In recent studies, knowledge distillation-based methods have been widely used in unsupervised anomaly detection to…

Machine Learning · Computer Science 2024-07-02 Rui Cao , Shijie Xue , Jindong Li , Qi Wang , Yi Chang

Does the intrinsic curvature of complex networks hold the key to unveiling graph anomalies that conventional approaches overlook? Reconstruction-based graph anomaly detection (GAD) methods overlook such geometric outliers, focusing only on…

Machine Learning · Computer Science 2025-06-06 Karish Grover , Geoffrey J. Gordon , Christos Faloutsos

Normalizing flows are prominent deep generative models that provide tractable probability distributions and efficient density estimation. However, they are well known to fail while detecting Out-of-Distribution (OOD) inputs as they directly…

Machine Learning · Computer Science 2021-11-17 Nishant Kumar , Pia Hanfeld , Michael Hecht , Michael Bussmann , Stefan Gumhold , Nico Hoffmann

Graph anomaly detection aims to identify irregular patterns in graph-structured data. Most unsupervised GNN-based methods rely on the homophily assumption that connected nodes share similar attributes. However, real-world graphs often…

Machine Learning · Computer Science 2026-04-20 Zehao Wang , Lanjun Wang