Privacy has raised considerable concerns recently, especially with the advent of information explosion and numerous data mining techniques to explore the information inside large volumes of data. In this context, a new distributed learning paradigm termed federated learning becomes prominent recently to tackle the privacy issues in distributed learning, where only learning models will be transmitted from the distributed nodes to servers without revealing users' own data and hence protecting the privacy of users. In this paper, we propose a horizontal federated XGBoost algorithm to solve the federated anomaly detection problem, where the anomaly detection aims to identify abnormalities from extremely unbalanced datasets and can be considered as a special classification problem. Our proposed federated XGBoost algorithm incorporates data aggregation and sparse federated update processes to balance the tradeoff between privacy and learning performance. In particular, we introduce the virtual data sample by aggregating a group of users' data together at a single distributed node. We compute parameters based on these virtual data samples in the local nodes and aggregate the learning model in the central server. In the learning model upgrading process, we focus more on the wrongly classified data before in the virtual sample and hence to generate sparse learning model parameters. By carefully controlling the size of these groups of samples, we can achieve a tradeoff between privacy and learning performance. Our experimental results show the effectiveness of our proposed scheme by comparing with existing state-of-the-arts.
Anomaly detection @cite_9 is the identification of events or observations that do not match the expected pattern or other items in the dataset (i.e., outliers) during data mining. Outliers can be divided into point exceptions, context exceptions, and collective exceptions @cite_4 . Anomaly detection methods include SMOTE algorithm @cite_21 and various machine learning models, such as K-Nearest Neighbors algorithm @cite_10 , Random Forest @cite_15 , Support Vector Machine (SVM) @cite_11 , Gradient Boosting Classification Tree (GBT) @cite_5 , XGBoost @cite_19 , and deep learning neural network models @cite_8 . In this paper, a point exception of fraud detection in credit card transactions will be focused and the dataset of credit card transactions will be used to train the model.
@cite_4 @cite_8 @cite_9 @cite_21 @cite_19 @cite_5 @cite_15 @cite_10 @cite_11
2531279268 2803446235 2143559571 2044019460
Anomaly detection is still a challenging task for video surveillance due to complex environments and unpredictable human behaviors. Most existing approaches train offline detectors using manually labeled data and predefined parameters, and are hard to model changing scenes. This paper introduces a neural network based model called online Growing Neural Gas (online GNG) to perform an unsupervised learning. Unlike a parameter-fixed GNG, our model updates learning parameters continuously, for which we propose several online neighbor-related strategies. Specific operations, namely neuron insertion, deletion, learning rate adaptation and stopping criteria selection, get upgraded to online modes. In the anomaly detection stage, the behavior patterns far away from our model are labeled as anomalous, for which far away is measured by a time-varying threshold. Experiments are implemented on three surveillance datasets, namely UMN, UCSD Ped1 Ped2 and Avenue dataset. All datasets have changing scenes due to mutable crowd density and behavior types. Anomaly detection results show that our model can adapt to the current scene rapidly and reduce false alarms while still detecting most anomalies. Quantitative comparisons with 12 recent approaches further confirm our superiority. HighlightsOnline GNG employs neighbor-related strategies to adjust dominant learning parameters in a fully automated way.Online GNG can estimate the learning efficiency and adjust the network size to fit the unstable data space dynamically.Online GNG effectively reduces the false alarms and leak detections caused by model aging which frequently happens in changing surveillance scenes. Anomaly detection is a classical problem in computer vision, namely the determination of the normal from the abnormal when datasets are highly biased towards one class (normal) due to the insufficient sample size of the other class (abnormal). While this can be addressed as a supervised learning problem, a significantly more challenging problem is that of detecting the unknown unseen anomaly case that takes us instead into the space of a one-class, semi-supervised learning paradigm. We introduce such a novel anomaly detection model, by using a conditional generative adversarial network that jointly learns the generation of high-dimensional image space and the inference of latent space. Employing encoder-decoder-encoder sub-networks in the generator network enables the model to map the input image to a lower dimension vector, which is then used to reconstruct the generated output image. The use of the additional encoder network maps this generated image to its latent representation. Minimizing the distance between these images and the latent vectors during training aids in learning the data distribution for the normal samples. As a result, a larger distance metric from this learned data distribution at inference time is indicative of an outlier from that distribution - an anomaly. Experimentation over several benchmark datasets, from varying domains, shows the model efficacy and superiority over previous state-of-the-art approaches. Anomaly detection is being regarded as an unsupervised learning task as anomalies stem from adversarial or unlikely events with unknown distributions. However, the predictive performance of purely unsupervised anomaly detection often fails to match the required detection rates in many tasks and there exists a need for labeled data to guide the model generation. Our first contribution shows that classical semi-supervised approaches, originating from a supervised classifier, are inappropriate and hardly detect new and unknown anomalies. We argue that semi-supervised anomaly detection needs to ground on the unsupervised learning paradigm and devise a novel algorithm that meets this requirement. Although being intrinsically non-convex, we further show that the optimization problem has a convex equivalent under relatively mild assumptions. Additionally, we propose an active learning strategy to automatically filter candidates for labeling. In an empirical study on network intrusion detection data, we observe that the proposed learning methodology requires much less labeled data than the state-of-the-art, while achieving higher detection accuracies. Anomaly detection refers to the identification of patterns in a dataset that do not conform to expected patterns. Depending on the domain, the non-conformant patterns are assigned various tags, e.g. anomalies, outliers, exceptions, malwares and so forth. Online anomaly detection aims to detect anomalies in data flowing in a streaming fashion. Such stream data is commonplace in today's cloud data centers that house a large array of virtual machines(VM) producing vast amounts of performance data in real-time. Sophisticated detection mechanism will likely entail collation of data from heterogeneous sources with diversified data format and semantics. Therefore, detection of performance anomaly in this context requires a distributed framework with high throughput and low latency. Apache Spark is one such framework that represents the bleeding-edge amongst its contemporaries. In this paper, we have taken up the challenge of anomaly detection in VMware based cloud data centers. We have employed a Chi-square based statistical anomaly detection technique in Spark. We have demonstrated how to take advantage of the high processing power of Spark to perform anomaly detection on heterogeneous data using statistical techniques. Our approach is optimally designed to cope with the heterogeneity of input data streams and the experiments we conducted testify to its efficacy in online anomaly detection.