Deep Contrastive One-Class Time Series Anomaly Detection
Beihang University（北京航空航天大学）；University of New South Wales（新南威尔士大学）；Hangzhou Innovation Institute, Beihang University（北京航空航天大学杭州创新研究院）；China University of Geosciences in Beijing（中国地质大学（北京））
Rui Wang, Chongwei Liu, Xudong Mou, Kai Gao, Xiaohui Guo, Pin Liu, Tianyu Wo, Xudong Liu
The accumulation of time-series data and the absence of labels make time-series Anomaly Detection (AD) a self-supervised deep learning task. Single-normality-assumption-based methods, which reveal only a certain aspect of the whole normality, are incapable of tasks involved with a large number of anomalies. Specifically, Contrastive Learning (CL) methods distance negative pairs, many of which consist of both normal samples, thus reducing the AD performance. Existing multi-normality-assumption-based methods are usually two-staged, firstly pre-training through certain tasks whose target may differ from AD, limiting their performance. To overcome the shortcomings, a deep Contrastive One-Class Anomaly detection method of time series (COCA) is proposed by authors, following the normality assumptions of CL and one-class classification. It treats the original and reconstructed representations as the positive pair of negative-sample-free CL, namely "sequence contrast". Next, invariance terms and variance terms compose a contrastive one-class loss function in which the loss of the assumptions is optimized by invariance terms simultaneously and the "hypersphere collapse" is prevented by variance terms. In addition, extensive experiments on two real-world time-series datasets show the superior performance of the proposed method achieves state-of-the-art.
EAGLE: Contrastive Learning for Efficient Graph Anomaly Detection
Institute of Innovation, Science and Sustainability, Federation University Australia（创新、科学与可持续性研究所，联邦大学澳大利亚）；School of Software, Dalian University of Technology（软件学院，大连理工大学）；Computing Center, Anshan Normal University（计算机中心，鞍山师范学院）
DACAD: Domain Adaptation Contrastive Learning for Anomaly Detection in Multivariate Time Series
Department of Data Science and AI, Monash University（数据科学与人工智能系，墨尔本大学）；Department of Computer Science, University of Oxford（计算机科学系，牛津大学）；IBM T. J. Watson Research Center（IBM T. J. Watson研究中心）；Squirrel Ai Learning（Squirrel Ai Learning公司）；School of ICT, Griffith University（信息科技学院，格里菲斯大学）
Reliable detection of anomalies is crucial when deploying machine learning models in practice, but remains challenging due to the lack of labeled data. To tackle this challenge, contrastive learning approaches are becoming increasingly popular, given the impressive results they have achieved in self-supervised representation learning settings. However, while most existing contrastive anomaly detection and segmentation approaches have been applied to images, none of them can use the contrastive losses directly for both anomaly detection and segmentation. In this paper, we close this gap by maki…
ContraLog: Log File Anomaly Detection with Contrastive Learning and Masked Language Modeling
Munich Center for Machine Learning（慕尼黑机器学习中心）；LMU München（慕尼黑大学）；German Research Center for Environmental Health, Helmholtz Zentrum München（德国环境健康研究中心，亥姆霍兹慕尼黑中心）
DConAD: A Differencing-based Contrastive Representation Learning Framework for Time Series Anomaly Detection
University of Chinese Academy of Science（中国科学院大学）；Tsinghua University（清华大学）；Shanghai University of International Business and Economics（上海国际商务经济学院）；Northeast Normal University（东北师范大学）；Fuzhou University（福州市大学）；Hubei University（湖北大学）；Hainan University（海南大学）；Northeastern University（东北大学）
Contrastive Representation Modeling for Anomaly Detection
Technology Innovation Institute, Abu Dhabi, UAE（阿布扎比技术创新研究所）；Computer Science Department, Khalifa University of Science and Technology, Abu Dhabi, UAE（科技学院计算机科学系）
Anomaly detection on the attributed network has recently received increasing attention in many research fields, such as cybernetic anomaly detection and financial fraud detection. With the wide application of deep learning on graph representations, existing approaches choose to apply euclidean graph encoders as their backbone, which may lose important hierarchical information, especially in complex networks. To tackle this problem, we propose an efficient anomaly detection framework using hyperbolic self-supervised contrastive learning. Specifically, we first conduct the data augmentation by p…
Monash University（莫纳什大学）；Singapore Management University（新加坡管理大学）；VinUniversity（威宁大学）；The University of Melbourne（墨尔本大学）
Cross-domain graph anomaly detection (CD-GAD) describes the problem of detecting anomalous nodes in an unlabelled target graph using auxiliary, related source graphs with labelled anomalous and normal nodes. Although it presents a promising approach to address the notoriously high false positive issue in anomaly detection, little work has been done in this line of research. There are numerous domain adaptation methods in the literature, but it is difficult to adapt them for GAD due to the unknown distributions of the anomalies and the complex node relations embedded in graph data. To this end,…
Rethinking Contrastive Learning in Graph Anomaly Detection: A Clean-View Perspective
College of Intelligence and Computing, Tianjin University（天津大学智能计算学院）；Guangdong Laboratory of Artificial Intelligence and Digital Economy (SZ)（广东人工智能与数字经济实验室（深圳））；Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences（深圳先进技术研究院，中国科学院）
RoCA: Robust Contrastive One-class Time Series Anomaly Detection with Contaminated Data
School of Computer Science and Engineering, Beihang University（北京航空航天大学计算机科学与工程学院）；Zhongguancun Laboratory（中关村实验室）；School of Software, Beihang University（北京航空航天大学软件学院）
NUS（新加坡国立大学）；Institute for Infocomm Research (IR) A*STAR（新加坡科技研究局资讯通信研究院）
Anomaly detection in multi-variate time series (MVTS) data is a huge challenge as it requires simultaneous representation of long term temporal dependencies and correlations across multiple variables. More often, this is solved by breaking the complexity through modeling one dependency at a time. In this paper, we propose a Time-series Representational Learning through Contrastive Predictive Coding (TRL-CPC) towards anomaly detection in MVTS data. First, we jointly optimize an encoder, an auto-regressor and a non-linear transformation function to effectively learn the representations of the MV…
Unsupervised domain adaptation (UDA) aims at learning a machine learning model using a labeled source domain that performs well on a similar yet different, unlabeled target domain. UDA is important in many applications such as medicine, where it is used to adapt risk scores across different patient cohorts. In this paper, we develop a novel framework for UDA of time series data, called CLUDA. Specifically, we propose a contrastive learning framework to learn contextual representations in multivariate time series, so that these preserve label information for the prediction task. In our framewor…
RED-F: Reconstruction-Elimination based Dual-stream Contrastive Forecasting for Multivariate Time Series Anomaly Prediction
School of Computer Science (National Pilot Software Engineering School), Beijing University of Posts and Telecommunications（计算机学院（国家级试点软件工程学院），北京邮电大学）；China Telecom Research Institute Beijing（中国电信研究院北京分院）；Department of Computer Science, Missouri University of Science and Technology（计算机学院，密苏里科技大学）
Frequency-Masked Embedding Inference: A Non-Contrastive Approach for Time Series Representation Learning
School of Intelligence Science and Technology, University of Science and Technology Beijing（北京科技大学智能科学与技术学院）；Institute of Artificial Intelligence, University of Science and Technology Beijing（北京科技大学人工智能研究院）
SenseTime Research（商汤科技研究院）；Institute of Computing Technology, Chinese Academy of Sciences（中国科学院计算技术研究所）；University of Chinese Academy of Sciences（中国科学院大学）；University of California, Los Angeles（加州大学洛杉矶分校）
The essence of unsupervised anomaly detection is to learn the compact distribution of normal samples and detect outliers as anomalies in testing. Meanwhile, the anomalies in real-world are usually subtle and fine-grained in a high-resolution image especially for industrial applications. Towards this end, we propose a novel framework for unsupervised anomaly detection and localization. Our method aims at learning dense and compact distribution from normal images with a coarse-to-fine alignment process. The coarse alignment stage standardizes the pixel-wise position of objects in both image and …
Shandong University（山东大学）；Joint SDU-NTU Centre for Artificial Intelligence Research (C-FAIR), Shandong University（山东大学-南洋理工大学联合人工智能研究中心（C-FAIR））；Lund University（隆德大学）；Nanyang Technological University（南洋理工大学）
Learning semantic-rich representations from raw unlabeled time series data is critical for downstream tasks such as classification and forecasting. Contrastive learning has recently shown its promising representation learning capability in the absence of expert annotations. However, existing contrastive approaches generally treat each instance independently, which leads to false negative pairs that share the same semantics. To tackle this problem, we propose MHCCL, a Masked Hierarchical Cluster-wise Contrastive Learning model, which exploits semantic information obtained from the hierarchical …
Predictive Reasoning with Augmented Anomaly Contrastive Learning for Compositional Visual Relations
School of Computer Science, University of Nottingham Ningbo China（诺丁汉大学宁波校区计算机科学学院）；Institute of Biomedical Engineering, Ningbo institute of materials technology and engineering, Chinese Academy of Sciences（中国科学院宁波材料技术与工程研究所生物医学工程研究所）；School of Electrical & Electronic Engineering, Nanyang Technological University（南洋理工大学电子与电气工程学院）
Entropy Causal Graphs for Multivariate Time Series Anomaly Detection
Institute of Innovation, Science and Sustainability（创新、科学与可持续性研究所）；Federation University Australia, Australia and CSIRO's Data61（联邦大学澳大利亚分校和CSIRO的数据61）；Federation University Australia（联邦大学澳大利亚分校）；RMIT University（皇家墨尔本理工学院）
FreRA: A Frequency-Refined Augmentation for Contrastive Learning on Time Series Classification
Alibaba-NTU Singapore Joint Research Institute（阿里巴巴-国立科技大学新加坡联合研究机构）；College of Computing and Data Science, Nanyang Technological University Singapore（国立科技大学新加坡计算机与数据科学学院）；CFAR, A*STAR Singapore（新加坡A*STAR医学研究中心）
As large-scale time-series data can easily be found in real-world applications, multivariate time-series anomaly detection has played an essential role in diverse industries. It enables productivity improvement and maintenance cost reduction by preventing malfunctions and detecting anomalies based on time-series data. However, multivariate time-series anomaly detection is challenging because real-world time-series data exhibit complex temporal dependencies. For this task, it is crucial to learn a rich representation that effectively contains the nonlinear temporal dynamics of normal behavior. …
University of Oxford（牛津大学）；AWS AI Labs（AWS人工智能实验室）
We introduce Neural Contextual Anomaly Detection (NCAD), a framework for anomaly detection on time series that scales seamlessly from the unsupervised to supervised setting, and is applicable to both univariate and multivariate time series. This is achieved by effectively combining recent developments in representation learning for multivariate time series, with techniques for deep anomaly detection originally developed for computer vision that we tailor to the time series setting. Our window-based approach facilitates learning the boundary between normal and anomalous classes by injecting gen…
Time series anomaly detection is a challenging problem due to the complex temporal dependencies and the limited label data. Although some algorithms including both traditional and deep models have been proposed, most of them mainly focus on time-domain modeling, and do not fully utilize the information in the frequency domain of the time series data. In this paper, we propose a Time-Frequency analysis based time series Anomaly Detection model, or TFAD for short, to exploit both time and frequency domains for performance improvement. Besides, we incorporate time series decomposition and data au…
Data Science Group, IBS（基础科学研究院数据科学组）；School of Computing, KAIST（韩国科学技术院计算学院）
Anomaly detection aims at identifying deviant instances from the normal data distribution. Many advances have been made in the field, including the innovative use of unsupervised contrastive learning. However, existing methods generally assume clean training data and are limited when the data contain unknown anomalies. This paper presents Elsa, a novel semi-supervised anomaly detection approach that unifies the concept of energy-based models with unsupervised contrastive learning. Elsa instills robustness against any data contamination by a carefully designed fine-tuning step based on the new …
UiT the Arctic University of Norway（特罗姆瑟大学-挪威北极圈大学）；Norwegian Computing Center（挪威计算中心）；University Hospital of North Norway（北挪威大学医院）
The lack of labeled data is a key challenge for learning useful representation from time series data. However, an unsupervised representation framework that is capable of producing high quality representations could be of great value. It is key to enabling transfer learning, which is especially beneficial for medical applications, where there is an abundance of data but labeling is costly and time consuming. We propose an unsupervised contrastive learning framework that is motivated from the perspective of label smoothing. The proposed approach uses a novel contrastive loss that naturally expl…
Tencent Company（腾讯公司）；National University of Singapore（新加坡国立大学）
Time series anomaly detection is usually formulated as finding outlier data points relative to some usual data, which is also an important problem in industry and academia. To ensure systems working stably, internet companies, banks and other companies need to monitor time series, which is called KPI (Key Performance Indicators), such as CPU used, number of orders, number of online users and so on. However, millions of time series have several shapes (e.g. seasonal KPIs, KPIs of timed tasks and KPIs of CPU used), so that it is very difficult to use a simple statistical model to detect anomaly …
