Single Node Injection Label Specificity Attack on Graph Neural Networks via Reinforcement Learning

TL;DR

This paper introduces G$^2$-SNIA, a reinforcement learning-based method for single node injection attacks on GNNs that effectively manipulates node classification in black-box settings with limited attack budgets.

Contribution

It proposes a gradient-free, generalizable attack framework using reinforcement learning to inject a single malicious node, outperforming existing methods in realistic black-box scenarios.

Findings

G$^2$-SNIA outperforms state-of-the-art baselines in benchmark datasets.

The method achieves diverse attack goals with limited attack budgets.

G$^2$-SNIA's solutions are comparable to white-box attack methods.

Abstract

Graph neural networks (GNNs) have achieved remarkable success in various real-world applications. However, recent studies highlight the vulnerability of GNNs to malicious perturbations. Previous adversaries primarily focus on graph modifications or node injections to existing graphs, yielding promising results but with notable limitations. Graph modification attack~(GMA) requires manipulation of the original graph, which is often impractical, while graph injection attack~(GIA) necessitates training a surrogate model in the black-box setting, leading to significant performance degradation due to divergence between the surrogate architecture and the actual victim model. Furthermore, most methods concentrate on a single attack goal and lack a generalizable adversary to develop distinct attack strategies for diverse goals, thus limiting precise control over victim model behavior in real-world scenarios. To address these issues, we present a gradient-free generalizable adversary that injects a single malicious node to manipulate the classification result of a target node in the black-box evasion setting. We propose Gradient-free Generalizable Single Node Injection Attack, namely G$^2$-SNIA, a reinforcement learning framework employing Proximal Policy Optimization. By directly querying the victim model, G$^2$-SNIA learns patterns from exploration to achieve diverse attack goals with extremely limited attack budgets. Through comprehensive experiments over three acknowledged benchmark datasets and four prominent GNNs in the most challenging and realistic scenario, we demonstrate the superior performance of our proposed G$^2$-SNIA over the existing state-of-the-art baselines. Moreover, by comparing G$^2$-SNIA with multiple white-box evasion baselines, we confirm its capacity to generate solutions comparable to those of the best adversaries.