ANOMALY DETECTION IN ETHEREUM TRANSACTIONS USING GRAPH NEURAL NETWORKS AND EXPLAINABLE AI

Sajidah Shahadha Mahmood, Maher Shahatha Mahmood

Abstract: As the blockchain technology and decentralized finance have grown rapidly, the number of fraudulent and anomalous activities has risen. The paper suggests a detectable graph-based anomaly detection system to detect suspicious Ethereum transactions. One 10,000 Ethereum transactions dataset was gathered through the Etherscan API within a 14 hour observation period and a directed transaction graph was created out of that dataset, where 14 behavioral node features were engineered. Three graph neural network (GNN) models, namely, Graph Convolutional Network (GCN), Graph Attention Network (GAT), and GraphSAGE, were checked on 5-fold cross-validation, and compared to three standard baseline classifiers, which are Logistic Regression, Random Forest, and XGBoost. GraphSAGE had the highest overall accuracy of 82.32, F1-score of 0.6389, and ROC-AUC of 0.8202, and GCN and GAT had near-zero recall on the minority class. XGBoost was the best baseline with the highest accuracy (94.41) but with significantly lower recall (0.2766) and F1-score (0.3801) compared to GraphSAGE, which is indicative of graph-based models being more balanced in precision and recall in detecting anomalies with class imbalance. The Local Interpretable Model-agnostic Explanations (LIME) showed outgoing transaction value features and account balance to be most important predictors of anomalous behavior. The results establish the promise of using GNNs in conjunction with explainable AI to secure blockchains, as well as reveal the challenges such as the class imbalance and ground-truth verified labels.

Keywords: Anomaly Detection, Blockchain Security, Ethereum, Graph Neural Networks, Explainable AI, LIME

DOI: 10.24874/PES08.02A.002

Recieved: 16.02.2026  Revised: 01.06.2026  Accepted: 16.06.2026  
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