Self-Discriminative Modeling for Anomalous Graph Detection

TL;DR

This paper introduces a self-discriminative framework for detecting anomalous graphs by training a classifier with pseudo-anomalous graphs generated alongside normal graphs, achieving superior results without using true anomalies.

Contribution

The paper proposes a novel self-discriminative modeling approach that jointly trains a discriminator and pseudo-anomalous graphs for unsupervised anomalous graph detection.

Findings

Significant AUC improvements over state-of-the-art baselines.

Effective detection on large-scale imbalanced datasets.

Unsupervised method outperforms supervised algorithms.

Abstract

This paper studies the problem of detecting anomalous graphs using a machine learning model trained on only normal graphs, which has many applications in molecule, biology, and social network data analysis. We present a self-discriminative modeling framework for anomalous graph detection. The key idea, mathematically and numerically illustrated, is to learn a discriminator (classifier) from the given normal graphs together with pseudo-anomalous graphs generated by a model jointly trained, where we never use any true anomalous graphs and we hope that the generated pseudo-anomalous graphs interpolate between normal ones and (real) anomalous ones. Under the framework, we provide three algorithms with different computational efficiencies and stabilities for anomalous graph detection. The three algorithms are compared with several state-of-the-art graph-level anomaly detection baselines on nine popular graph datasets (four with small size and five with moderate size) and show significant improvement in terms of AUC. The success of our algorithms stems from the integration of the discriminative classifier and the well-posed pseudo-anomalous graphs, which provide new insights for anomaly detection. Moreover, we investigate our algorithms for large-scale imbalanced graph datasets. Surprisingly, our algorithms, though fully unsupervised, are able to significantly outperform supervised learning algorithms of anomalous graph detection. The corresponding reason is also analyzed.