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1. Urban Anomalies: A Simulated Human Mobility Dataset with Injected Anomalies

   https://doi.org/10.1145/3681765.3698459  

   Amiri, Hossein; Kong, Ruochen; Züfle, Andreas (October 2024, ACM)

   Human mobility anomaly detection based on location is essential in areas such as public health, safety, welfare, and urban planning. Developing models and approaches for location-based anomaly detection requires a comprehensive dataset. However, privacy concerns and the absence of ground truth hinder the availability of publicly available datasets. With this paper, we provide extensive simulated human mobility datasets featuring various anomaly types created using an existing Urban Patterns of Life Simulation. To create these datasets, we inject changes in the logic of individual agents to change their behavior. Specifically, we create four of anomalous agent behavior by (1) changing the agents’ appetite (causing agents to have meals more frequently), (2) changing their group of interest (causing agents to interact with different agents from another group). (3) changing their social place selection (causing agents to visit different recreational places) and (4) changing their work schedule (causing agents to skip work), For each type of anomaly, we use three degrees of behavioral change to tune the difficulty of detecting the anomalous agents. To select agents to inject anomalous behavior into, we employ three methods: (1) Random selection using a centralized manipulation mechanism, (2) Spread based selection using an infectious disease model, and (3) through exposure of agents to a specific location. All datasets are split into normal and anomalous phases. The normal phase, which can be used for training models of normalcy, exhibits no anomalous behavior. The anomalous phase, which can be used for testing for anomalous detection algorithm, includes ground truth labels that indicate, for each five-minute simulation step, which agents are anomalous at that time. Datasets are generated using the maps (roads and buildings) for Atlanta and Berlin having 1k agents in each simulation. All datasets are openly available at https://osf.io/dg6t3/. Additionally, we provide instructions to regenerate the data for other locations and numbers of agents. 

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2. Latent Diffusion Based Multi-class Anomaly Detection.

   Wang, C; Tavakkoli, A (December 2023, ISVC, Springer)

   The unsupervised anomaly detection problem holds great importance but remains challenging to address due to the myriad of data possibilities in our daily lives. Currently, distinct models are trained for different scenarios. In this work, we introduce a reconstruction-based anomaly detection structure built on the Latent Space Denoising Diffusion Probabilistic Model (LDM). This structure effectively detects anomalies in multi-class situations. When normal data comprises multiple object categories, existing reconstruction models often learn identical patterns. This leads to the successful reconstruction of both normal and anomalous data based on these patterns, resulting in the inability to distinguish anomalous data. To address this limitation, we implemented the LDM model. Its process of adding noise effectively disrupts identical patterns. Additionally, this advanced image generation model can generate images that deviate from the input. We have further proposed a classification model that compares the input with the reconstruction results, tapping into the generative power of the LDM model. Our structure has been tested on the MNIST and CIFAR-10 datasets, where it surpassed the performance of state-of-the-art reconstruction-based anomaly detection models. 

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3. Traffic Anomaly Detection Via Conditional Normalizing Flow

   https://doi.org/10.1109/ITSC55140.2022.9922061  

   Kang, Zhuangwei; Mukhopadhyay, Ayan; Gokhale, Aniruddha; Wen, Shijie; Dubey, Abhishek (October 2022, 2022 IEEE 25th International Conference on Intelligent Transportation Systems (ITSC))

   Traffic congestion anomaly detection is of paramount importance in intelligent traffic systems. The goals of transportation agencies are two-fold: to monitor the general traffic conditions in the area of interest and to locate road segments under abnormal congestion states. Modeling congestion patterns can achieve these goals for citywide roadways, which amounts to learning the distribution of multivariate time series (MTS). However, existing works are either not scalable or unable to capture the spatial-temporal information in MTS simultaneously. To this end, we propose a principled and comprehensive framework consisting of a data-driven generative approach that can perform tractable density estimation for detecting traffic anomalies. Our approach first clusters segments in the feature space and then uses conditional normalizing flow to identify anomalous temporal snapshots at the cluster level in an unsupervised setting. Then, we identify anomalies at the segment level by using a kernel density estimator on the anomalous cluster. Extensive experiments on synthetic datasets show that our approach significantly outperforms several state-of-the-art congestion anomaly detection and diagnosis methods in terms of Recall and F1-Score. We also use the generative model to sample labeled data, which can train classifiers in a supervised setting, alleviating the lack of labeled data for anomaly detection in sparse settings. 

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4. Generative Anomaly Detection for Time Series Datasets

   Kang, Zhuangwei; Mukhopadhyay, Ayan; Gokhale, Aniruddha; Wen, Shijie and (January 2022, ITSC)

   Traffic congestion anomaly detection is of paramount importance in intelligent traffic systems. The goals of transportation agencies are two-fold: to monitor the general traffic conditions in the area of interest and to locate road segments under abnormal congestion states. Modeling congestion patterns can achieve these goals for citywide roadways, which amounts to learning the distribution of multivariate time series (MTS). However, existing works are either not scalable or unable to capture the spatial-temporal information in MTS simultaneously. To this end, we propose a principled and comprehensive framework consisting of a data-driven generative approach that can perform tractable density estimation for detecting traffic anomalies. Our approach first clusters segments in the feature space and then uses conditional normalizing flow to identify anomalous temporal snapshots at the cluster level in an unsupervised setting. Then, we identify anomalies at the segment level by using a kernel density estimator on the anomalous cluster. Extensive experiments on synthetic datasets show that our approach significantly outperforms several state-of-the-art congestion anomaly detection and diagnosis methods in terms of Recall and F1-Score. We also use the generative model to sample labeled data, which can train classifiers in a supervised setting, alleviating the lack of labeled data for anomaly detection in sparse settings. 

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5. Anomaly Detection Using Support Vector Machines for Time Series Data

   Yokkampon, U; Chumkamon, S.; Mowshowitz, A; Fujisawa, R.; Hayashi, E. (June 2021, Journal of robotics networking and artificial life)

   null (Ed.)

   Analysis of large data sets is increasingly important in business and scientific research. One of the challenges in such analysis stems from uncertainty in data, which can produce anomalous results. This paper proposes a method for detecting an anomaly in time series data using a Support Vector Machine (SVM). Three different kernels of the SVM are analyzed to predict anomalies in the UCR time series benchmark data sets. Comparison of the three kernels shows that the defined parameter values of the Radial Basis Function (RBF) kernel are critical for improving the validity and accuracy in anomaly detection. Our results show that the RBF kernel of the SVM can be used to advantage in detecting anomalies. 

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