arXiv Machine Learning By Honglin Gao, Junhao Ren, Lan Zhao, Yue Yang, Peilin Du, Jindong Chang, Gaoxi Xiao

Blackknife: Query-Free Black-Box Rewiring Attacks on Heterogeneous Graph Neural Networks

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Blackknife is a query‑free, strict black‑box evasion attack designed for heterogeneous graph neural networks (HGNNs). It relies solely on observing one‑hop structures, ground‑truth labels, and raw features of target nodes, without using victim‑model outputs. The attack trains a shared surrogate on observable edges and relation types, then optimizes structural perturbations via continuous relaxation and projected gradient ascent, preserving node degrees while adding a cosine‑similarity penalty and adaptive structural classifier for regularization. Experiments show competitive success rates across multiple victim architectures and defense settings, revealing HGNN vulnerabilities under restricted graph access and query‑free attack generation.

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arXiv AI
Sep 11

Kernel-Complexity Edge Sanitization for Training-Free Defense against Structural Graph Attacks

Kernel-Complexity Edge Sanitization (KCES) is a training‑free, model‑agnostic defense for Graph Neural Networks that identifies and removes edges with high Kernel‑Complexity (KC) scores, which are indicative of structural influence on the graph kernel complexity metric. KCES leverages a theoretical upper bound on GNN test error derived from the graph Gram matrix to compute edge‑specific KC scores, pruning edges that are empirically enriched with adversarial perturbations. The method is computationally efficient, scalable to large graphs, and consistently outperforms representative robust baselines across diverse attack settings without requiring retraining.

By Yaning Jia, Shenyang Deng, Yaoqing Yang, Chiyu Ma, Wenxuan Xu, Soroush Vosoughi