A Unifying Review of Deep and Shallow Anomaly Detection
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Abstract (arXiv)
Deep learning approaches to anomaly detection have recently improved the state of the art in detection performance on complex datasets such as large collections of images or text. These results have sparked a renewed interest in the anomaly detection problem and led to the introduction of a great variety of new methods. With the emergence of numerous such methods, including approaches based on generative models, one-class classification, and reconstruction, there is a growing need to bring methods of this field into a systematic and unified perspective. In this review we aim to identify the common underlying principles as well as the assumptions that are often made implicitly by various methods. In particular, we draw connections between classic 'shallow' and novel deep approaches and show how this relation might cross-fertilize or extend both directions. We further provide an empirical assessment of major existing methods that is enriched by the use of recent explainability techniques, and present specific worked-through examples together with practical advice. Finally, we outline critical open challenges and identify specific paths for future research in anomaly detection.
Key facts. Cited by 423 papers in the map (data through 7 Oct 2026). First posted on arXiv 24 Sep 2020.
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Citing papers per year: 2021: 58; 2022: 102; 2023: 86; 2024: 69; 2025: 58; 2026: 50.
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- 2021Generalized Out-of-Distribution Detection: A Surveycited by 796
- 2021CutPaste: Self-Supervised Learning for Anomaly Detection and Localizationcited by 529
- 2022Transformers in Time Series: A Surveycited by 489
- 2022SPot-the-Difference Self-Supervised Pre-training for Anomaly Detection and Segmentationcited by 397
- 2021CFLOW-AD: Real-Time Unsupervised Anomaly Detection with Localization via Conditional Normalizing Flowscited by 320
- 2023AnomalyCLIP: Object-agnostic Prompt Learning for Zero-shot Anomaly Detectioncited by 270
- 2022OpenOOD: Benchmarking Generalized Out-of-Distribution Detectioncited by 267
- 2021A Comprehensive Survey on Graph Anomaly Detection with Deep Learningcited by 230
- 2022ADBench: Anomaly Detection Benchmarkcited by 230
- 2022Out-of-Distribution Detection and Selective Generation for Conditional Language Modelscited by 193
- 2021A Unified Survey on Anomaly, Novelty, Open-Set, and Out-of-Distribution Detection: Solutions and Future Challengescited by 154
- 2022SHIFT: A Synthetic Driving Dataset for Continuous Multi-Task Domain Adaptationcited by 146
38 more
- 2021PixMix: Dreamlike Pictures Comprehensively Improve Safety Measurescited by 131
- 2021Natural Synthetic Anomalies for Self-Supervised Anomaly Detection and Localizationcited by 116
- 2021Truthful AI: Developing and governing AI that does not liecited by 109
- 2023DCdetector: Dual Attention Contrastive Representation Learning for Time Series Anomaly Detectioncited by 103
- 2021Neural Transformation Learning for Deep Anomaly Detection Beyond Imagescited by 98
- 2022Deep Isolation Forest for Anomaly Detectioncited by 90
- 2022Training OOD Detectors in their Natural Habitatscited by 86
- 2023On Diffusion Modeling for Anomaly Detectioncited by 71
- 2024A Survey on Visual Anomaly Detection: Challenge, Approach, and Prospectcited by 69
- 2021Does Your Dermatology Classifier Know What It Doesn't Know? Detecting the Long-Tail of Unseen Conditionscited by 68
- 2021FedAUX: Leveraging Unlabeled Auxiliary Data in Federated Learningcited by 67
- 2022Deep Learning for Unsupervised Anomaly Localization in Industrial Images: A Surveycited by 67
- 2024Real-Time Anomaly Detection and Reactive Planning with Large Language Modelscited by 67
- 2023Hierarchical Vector Quantized Transformer for Multi-class Unsupervised Anomaly Detectioncited by 66
- 2024Unpacking Failure Modes of Generative Policies: Runtime Monitoring of Consistency and Progresscited by 63
- 2021A Hierarchical Transformation-Discriminating Generative Model for Few Shot Anomaly Detectioncited by 60
- 2022Prototypical Residual Networks for Anomaly Detection and Localizationcited by 56
- 2024A Closer Look at AUROC and AUPRC under Class Imbalancecited by 56
- 2021Software for Dataset-wide XAI: From Local Explanations to Global Insights with Zennit, CoRelAy, and ViRelAycited by 53
- 2024AnomalyDINO: Boosting Patch-based Few-shot Anomaly Detection with DINOv2cited by 53
- 2022A Call to Reflect on Evaluation Practices for Failure Detection in Image Classificationcited by 51
- 2022Latent Outlier Exposure for Anomaly Detection with Contaminated Datacited by 48
- 2022TFAD: A Decomposition Time Series Anomaly Detection Architecture with Time-Frequency Analysiscited by 48
- 2022Raising the Bar in Graph-level Anomaly Detectioncited by 45
- 2021Out-of-Scope Intent Detection with Self-Supervision and Discriminative Trainingcited by 42
- 2021Neural Contextual Anomaly Detection for Time Seriescited by 42
- 2022Anomaly Detection-Inspired Few-Shot Medical Image Segmentation Through Self-Supervision With Supervoxelscited by 42
- 2023On Advantages of Mask-level Recognition for Outlier-aware Segmentationcited by 42
- 2021Unsupervised Deep Anomaly Detection for Multi-Sensor Time-Series Signalscited by 41
- 2022A Survey on Explainable Anomaly Detectioncited by 39
- 2024Generalized Out-of-Distribution Detection and Beyond in Vision Language Model Era: A Surveycited by 36
- 2025Failure Prediction at Runtime for Generative Robot Policiescited by 36
- 2022Exposing Outlier Exposure: What Can Be Learned From Few, One, and Zero Outlier Imagescited by 35
- 2021Confidence-based Out-of-Distribution Detection: A Comparative Study and Analysiscited by 34
- 2024Outlier detection by ensembling uncertainty with negative objectnesscited by 34
- 2022A System-Level View on Out-of-Distribution Data in Roboticscited by 33
- 2021Autoencoders for unsupervised anomaly detection in high energy physicscited by 32
- 2021Focus Your Distribution: Coarse-to-Fine Non-Contrastive Learning for Anomaly Detection and Localizationcited by 32
50 most cited of 423 All 423 (JSON)
- 2026Can We Predict Anomaly Detection Performance from Embedding-Space Geometry?22 Sep 2026
- 2026Robust Fault Detection in Mechanical Multimodal Time Series via Self-Supervised Cross-Modal Reconstruction14 Sep 2026
- 2026Risk and Anomaly Identification for Distribution Network Optimal Operation Based on Reinforcement Learning and Uncertainty Quantification3 Sep 2026
- 2026Generative multi-domain transfer learning for fault detection in data-scarce wind turbines31 Aug 2026
- 2026Low-Power, Neuromorphic, Acoustic Anomaly Detection for Persistent Machine Monitoring18 Aug 2026
- 2026Low Cost Two-Stage Fabric Defect Detection at the Edge12 Aug 2026
- 2026Federated Attention Autoencoders with a Stochastic Aggregation Scheme for Anomaly Detection9 Aug 2026
- 2026Attention, Anomalies! Handling Attention Layers in Unsupervised Federated Outlier Detection5 Aug 2026
- 2026Why Ranking Anomaly Detection Algorithms Isn't as Reliable as You May Think5 Aug 2026
- 2026Cross-Domain Industrial Fault Detection by Causal Mechanism Monitoring1 Aug 2026
- 2026Early Failure Prediction from Near-Anomaly Detection: A Proactive Approach29 Jul 2026
- 2026Group Equivariant Diffusion for Anomaly Detection in Computational Cytology28 Jul 2026
38 more
- 2026PriorProof: A Point-in-Time Measure of Technique Novelty for Formal Proofs18 Jul 2026
- 2026Modeling Normal Is All You Need: Joint Latent Clustering for Anomaly Detection in Multimodal Cyber-Physical Systems7 Jul 2026
- 2026Unsupervised Detection of Underground Tunnels in Ground-Penetrating Radar Using Depth-Restricted Reconstruction Scoring6 Jul 2026
- 2026ArcAD: Anomaly-Rectified Calibration for Cold-Start Supervised Anomaly Detection2 Jul 2026
- 2026RGLD: Randomized Global-Local Density Estimation for Tabular Anomaly Detection27 Jun 2026
- 2026PHOEBI: An Open-World Benchmark for Multi-Label Bacterial Identification in Phase-Contrast Microscopy22 Jun 2026
- 2026Beyond the Smile: A Hybrid Convolutional VAE for Crypto Volatility Surfaces15 Jun 2026
- 2026Rethinking Structural Anomaly Detection: From Decision Boundaries to Projection Operators13 Jun 2026
- 2026Profy: Interpretable Visualization of Expertise-Dependent Motor Skills Toward Supporting Piano Practice9 Jun 2026
- 2026LOTTERY: Learning from Reference-Only Samples in Two-Sample Testing under Size Asymmetry7 Jun 2026
- 2026Plan First, Judge Later, Run Better: A DMAIC-Inspired Agentic System for Industrial Anomaly Detection3 Jun 2026
- 2026Masked Diffusion Modeling for Anomaly Detection28 May 2026
- 2026Generalist Graph Anomaly Detection via Prototype-Based Distillation26 May 2026
- 2026When Rule Violations Are Rare: Chimera Training for Logical Anomaly Detection25 May 2026
- 2026Generative OOD-regularized Model-based Policy Optimization23 May 2026
- 2026Self-Supervised ConvLSTM for Fermi Large Area Telescope Transient Detection21 May 2026
- 2026Automatic Unsupervised Ensemble Outlier Model Selection--Extended Version15 May 2026
- 2026Debugging the Debuggers: Failure-Anchored Structured Recovery for Software Engineering Agents9 May 2026
- 2026uLEAD-TabPFN: Uncertainty-aware Dependency-based Anomaly Detection with TabPFN22 Apr 2026
- 2026Out of Context: Reliability in Multimodal Anomaly Detection Requires Contextual Inference14 Apr 2026
- 2026On-board Telemetry Monitoring in Autonomous Satellites: Challenges and Opportunities9 Apr 2026
- 2026Needle in a Haystack: One-Class Representation Learning for Detecting Rare Malignant Cells in Computational Cytology9 Apr 2026
- 2026Energy-Efficient Hierarchical Federated Anomaly Detection for the Internet of Underwater Things via Selective Cooperative Aggregation25 Mar 2026
- 2026Beyond a Single Signal: SPECTREG2, A Unified MultiExpert Anomaly Detector for Unknown Unknowns22 Mar 2026
- 2026ICLAD: In-Context Learning for Unified Tabular Anomaly Detection Across Supervision Regimes19 Mar 2026
- 2026RangeAD: Fast On-Model Anomaly Detection18 Mar 2026
- 2026Unsupervised Symbolic Anomaly Detection18 Mar 2026
- 2026FoMo X: Modular Explainability Signals for Outlier Detection Foundation Models18 Mar 2026
- 2026Anomaly detection in time-series via inductive biases in the latent space of conditional normalizing flows12 Mar 2026
- 2026Generative Latent Representations of 3D Brain MRI for Multi-Task Downstream Analysis in Down Syndrome14 Feb 2026
- 2026Contextual and Seasonal LSTMs for Time Series Anomaly Detection10 Feb 2026
- 2026Calibrating Tabular Anomaly Detection via Optimal Transport6 Feb 2026
- 2026AP-OOD: Attention Pooling for Out-of-Distribution Detection5 Feb 2026
- 2026ContraLog: Log File Anomaly Detection with Contrastive Learning and Masked Language Modeling3 Feb 2026
- 2026MRAD: Zero-Shot Anomaly Detection with Memory-Driven Retrieval31 Jan 2026
- 2026Analyzing Shapley Additive Explanations to Understand Anomaly Detection Algorithm Behaviors and Their Complementarity30 Jan 2026
- 2026VSCOUT: A Hybrid Variational Autoencoder Approach to Outlier Detection in High-Dimensional Retrospective Monitoring28 Jan 2026
- 2026Handcrafted Feature-Assisted One-Class Learning for Artist Authentication in Historical Drawings13 Jan 2026
50 newest of 423 All 423 (JSON)
- 2023On Diffusion Modeling for Anomaly Detectioncited by 71
- 2025Failure Prediction at Runtime for Generative Robot Policiescited by 36
- 2024Unsupervised Anomaly Detection via Masked Diffusion Posterior Samplingcited by 5
- 2024Adversarially Robust Industrial Anomaly Detection Through Diffusion Modelcited by 3
- 2026Masked Diffusion Modeling for Anomaly Detectioncited by 0
- 2026Group Equivariant Diffusion for Anomaly Detection in Computational Cytologycited by 0
- 2026Group Equivariant Diffusion for Anomaly Detection in Computational Cytology28 Jul 2026
- 2026Masked Diffusion Modeling for Anomaly Detection28 May 2026
- 2025Failure Prediction at Runtime for Generative Robot Policies10 Oct 2025
- 2024Adversarially Robust Industrial Anomaly Detection Through Diffusion Model9 Aug 2024
- 2024Unsupervised Anomaly Detection via Masked Diffusion Posterior Sampling27 Apr 2024
- 2023On Diffusion Modeling for Anomaly Detection29 May 2023
- 2024Retrieval Augmented Deep Anomaly Detection for Tabular Data30 Jan 2024
- 2021Generalized Out-of-Distribution Detection: A Surveycited by 796
- 2021CutPaste: Self-Supervised Learning for Anomaly Detection and Localizationcited by 529
- 2022Transformers in Time Series: A Surveycited by 489
- 2022SPot-the-Difference Self-Supervised Pre-training for Anomaly Detection and Segmentationcited by 397
- 2021CFLOW-AD: Real-Time Unsupervised Anomaly Detection with Localization via Conditional Normalizing Flowscited by 320
- 2023AnomalyCLIP: Object-agnostic Prompt Learning for Zero-shot Anomaly Detectioncited by 270
- 2022OpenOOD: Benchmarking Generalized Out-of-Distribution Detectioncited by 267
- 2021A Comprehensive Survey on Graph Anomaly Detection with Deep Learningcited by 230
- 2022ADBench: Anomaly Detection Benchmarkcited by 230
- 2022Out-of-Distribution Detection and Selective Generation for Conditional Language Modelscited by 193
- 2021A Unified Survey on Anomaly, Novelty, Open-Set, and Out-of-Distribution Detection: Solutions and Future Challengescited by 154
- 2022SHIFT: A Synthetic Driving Dataset for Continuous Multi-Task Domain Adaptationcited by 146
12 most cited of 403 All 403 (JSON)
- 2026Can We Predict Anomaly Detection Performance from Embedding-Space Geometry?22 Sep 2026
- 2026Robust Fault Detection in Mechanical Multimodal Time Series via Self-Supervised Cross-Modal Reconstruction14 Sep 2026
- 2026Risk and Anomaly Identification for Distribution Network Optimal Operation Based on Reinforcement Learning and Uncertainty Quantification3 Sep 2026
- 2026Generative multi-domain transfer learning for fault detection in data-scarce wind turbines31 Aug 2026
- 2026Low-Power, Neuromorphic, Acoustic Anomaly Detection for Persistent Machine Monitoring18 Aug 2026
- 2026Low Cost Two-Stage Fabric Defect Detection at the Edge12 Aug 2026
- 2026Federated Attention Autoencoders with a Stochastic Aggregation Scheme for Anomaly Detection9 Aug 2026
- 2026Attention, Anomalies! Handling Attention Layers in Unsupervised Federated Outlier Detection5 Aug 2026
- 2026Why Ranking Anomaly Detection Algorithms Isn't as Reliable as You May Think5 Aug 2026
- 2026Early Failure Prediction from Near-Anomaly Detection: A Proactive Approach29 Jul 2026
- 2026PriorProof: A Point-in-Time Measure of Technique Novelty for Formal Proofs18 Jul 2026
- 2026Modeling Normal Is All You Need: Joint Latent Clustering for Anomaly Detection in Multimodal Cyber-Physical Systems7 Jul 2026
12 newest of 403 All 403 (JSON)