One prevalent property we find empirically in real-world graph anomaly
detection (GAD) datasets is a one-class homophily, i.e., normal nodes tend to
have strong connection/affinity with each other, while the homophily in
abnormal nodes is significantly weaker than normal nodes. However, this
anomaly-discriminative property is ignored by existing GAD methods that are
typically built using a conventional anomaly detection objective, such as data
reconstruction. In this work, we explore this property to introduce a novel
unsupervised anomaly scoring measure for GAD -- local node affinity -- that
assigns a larger anomaly score to nodes that are less affiliated with their
neighbors, with the affinity defined as similarity on node
attributes/representations. We further propose Truncated Affinity Maximization
(TAM) that learns tailored node representations for our anomaly measure by
maximizing the local affinity of nodes to their neighbors. Optimizing on the
original graph structure can be biased by non-homophily edges (i.e., edges
connecting normal and abnormal nodes). Thus, TAM is instead optimized on
truncated graphs where non-homophily edges are removed iteratively to mitigate
this bias. The learned representations result in significantly stronger local
affinity for normal nodes than abnormal nodes. Extensive empirical results on
six real-world GAD datasets show that TAM substantially outperforms seven
competing models, achieving over 10% increase in AUROC/AUPRC compared to the
best contenders on challenging datasets. Our code will be made available at
https: //github.com/mala-lab/TAM-master/.

本文通过探索现实世界中图异常检测（GAD）数据集中的一类同态性质，引入了一种新颖的无监督异常评分度量 —— 本地节点亲和力，它将更少地与邻居关联的节点分配更大的异常评分，并提出了针对我们异常度量的定制节点表示方法 TAM，通过最大化节点对其邻居的本地亲和力进行优化。