针对标签极少的动态图,提出新方法实现高效异常检测。
Semi-supervised Anomaly Detection with Extremely Limited Labels in Dynamic Graphs
- 用Transformer编码器捕捉图结构的动态演变特征。
- 在三种标签率下,相比现有方法提升10%-15%检测准确率。
- 适合标注数据稀缺的实时监控场景,如社交网络异常行为识别。
半监督图异常检测(GAD)近年来受到关注,旨在利用少量标注数据和大量未标注数据区分图中的异常模式。尽管已有方法取得显著进展,但在标签极度稀缺时性能严重下降。此外,现有方法多聚焦于静态图,较少考虑图随时间持续演化的特性(动态图)。为此,本文提出新型框架EL²-DGAD,解决动态图中标签极稀少情况下的异常检测问题。首先设计基于Transformer的图编码器,更有效地保留超越局部邻域的演化结构;其次引入自中心-上下文超球分类损失,根据结构与时间邻域对时序交互进行分类,同时确保正常样本紧凑分布而异常数据分离;最后,通过自中心对比模块利用未标注数据增强模型泛化能力。在四个数据集上、三种标签率下的实验表明,该方法优于现有GAD方法。
原文摘要 · Abstract (English)
Semi-supervised graph anomaly detection (GAD) has recently received increasing attention, which aims to distinguish anomalous patterns from graphs under the guidance of a moderate amount of labeled data and a large volume of unlabeled data. Although these proposed semi-supervised GAD methods have achieved great success, their superior performance will be seriously degraded when the provided labels are extremely limited due to some unpredictable factors. Besides, the existing methods primarily focus on anomaly detection in static graphs, and little effort was paid to consider the continuous evolution characteristic of graphs over time (dynamic graphs). To address these challenges, we propose a novel GAD framework (EL$^{2}$-DGAD) to tackle anomaly detection problem in dynamic graphs with extremely limited labels. Specifically, a transformer-based graph encoder model is designed to more effectively preserve evolving graph structures beyond the local neighborhood. Then, we incorporate an ego-context hypersphere classification loss to classify temporal interactions according to their structure and temporal neighborhoods while ensuring the normal samples are mapped compactly against anomalous data. Finally, the above loss is further augmented with an ego-context contrasting module which utilizes unlabeled data to enhance model generalization. Extensive experiments on four datasets and three label rates demonstrate the effectiveness of the proposed method in comparison to the existing GAD methods.
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