Fraud detection is a typical data mining mission in the field of finance. In recent years, due to their capability of mining hidden associations between entities, graph neural networks (GNNs) have been widely applied to detect financial fraudsters. However, GNNs are fragile in their data aggregation process and will be attacked on purpose by fraudsters, therefore, some other pioneers have explored methods to enhance the robustness of GNN-based fraud detection models. But most existing models based on ideal settings, as real-life criminals tend to attack as far as they can reach, struggle to establish a unified effective approach for attacked and unattacked data of different scales in realistic scenarios. Furthermore, mainstream robust defense models indiscriminately modifying and truncating data will lose important information of the major unattacked parts in the original graph, which lowers their overall fraud detection precision. Therefore, in this work, we propose a novel generative fraud detection framework called GSRGNN. In particular, we first design a generative structure to obtain augmented node features. Then we prioritize the nodes with high degrees to create a more stable graph structure on local distributions. Finally, we pass the enhanced features and structure with the input ones in pairs through GNN layers, and create synthetic representations with abundant information and sufficient resistance to perturbations for subsequent fraud detection. In addition, we also design a novel black-box attack algorithm to realistically imitate the perturbations conducted by fraudsters on graph features and structure. Experiments on the world's leading electronic trading platform and public anti-fraud datasets demonstrate the outstanding performance of our proposed method compared with those state-of-the-art models, showing its superiority in precision and robustness on financial fraud detection missions.

Nowadays, as more users turn to WeChat Pay and other e-commerce platforms for transactions, an increasing number of fraudsters are being attracted to these platforms to conduct fraudulent activities, thereby stealing money. To address this issue, Graph Neural Networks (GNNs) have been widely adopted and have shown great success. However, with the rise of various transaction methods, users are increasingly engaging in multiple transaction networks, which creates a new scenario that requires models to detect fraud across these diverse networks. Unfortunately, current GNN-based fraud detection strategies often exhibit suboptimal performance and high time complexity in this evolving scenario, as they typically can handle only one transaction network at a time. Recently, advancements in graph prompt learning have demonstrated great success in managing various types of graph data and improving the generalization capabilities of the model, showing great promise for addressing this new fraud detection scenario. Nevertheless, the practical application of graph prompt learning in real-world fraud detection is still constrained, as they may exhibit bias when dealing with multiplex transaction networks and may fail to model the intrinsic relationships between nodes and their neighbors, which is crucial for effective fraud detection. To address these two challenges, we propose GPCF, an efficient graph pre-training and prompt learning framework. GPCF first incorporates a meta-learning-based strategy within neighbor-enhanced contrastive learning to pre-train the GNN model across diverse transaction networks. Then it aligns fraud detection tasks with the well-pre-trained model by simply fine-tuning the prompts. Extensive experiments demonstrate that GPCF achieves state-of-the-art results on open-access fraud and transaction datasets, as well as on real-world fraud datasets from WeChat Pay, one of the largest e-commerce platforms globally, showing the effectiveness of GPCF in practical applications.

Nowadays, Graph Fraud Detection (GFD) in financial scenarios has become an urgent research topic to protect online payment security. However, as organized crime groups are becoming more professional in real-world scenarios, fraudsters are employing more sophisticated camouflage strategies. Specifically, fraudsters disguise themselves by mimicking the behavioral data collected by platforms, ensuring that their key characteristics are consistent with those of benign users to a high degree, which we call Adaptive Camouflage. Consequently, this narrows the differences in behavioral traits between them and benign users within the platform's database, thereby making current GFD models lose efficiency. To address this problem, we propose a relation diffusion-based graph augmentation model Grad. In detail, Grad leverages a supervised graph contrastive learning module to enhance the fraud-benign difference and employs a guided relation diffusion generator to generate auxiliary homophilic relations from scratch. Based on these, weak fraudulent signals would be enhanced during the aggregation process, thus being obvious enough to be captured. Extensive experiments have been conducted on two real-world datasets provided by WeChat Pay, one of the largest online payment platforms with billions of users, and three public datasets. The results show that our proposed model Grad outperforms SOTA methods in both various scenarios, achieving at most 11.10% and 43.95% increases in AUC and AP, respectively.

Fraud detection, a classical data mining problem in finance applications, has risen in significance amid the intensifying confrontation between fraudsters and anti-fraud forces. Recently, an increasing number of criminals are constantly expanding the scope of fraud activities to covet the property of innocent victims. However, most existing approaches require abundant historical records to mine fraud patterns from financial transaction behaviors, thereby leading to significant challenges to protect minority groups, who are less involved in the modern financial market but also under the threat of fraudsters nowadays. Therefore, in this paper, we propose a novel community-enhanced multi-relation graph neural network-based model, named CMR-GNN, to address the important defects of existing fraud detection models in the tail effect situation. In particular, we first construct multiple types of relation graphs from historical transactions and then devise a clustering-based neural network module to capture diverse patterns from transaction communities. To mitigate information lacking tailed nodes, we proposed tailed-groups learning modules to aggregate features from similarly clustered subgraphs by graph convolution networks. Extensive experiments on both the real-world and public datasets demonstrate that our method not only surpasses the state-of-the-art baselines but also could effectively harness information within transaction communities while mitigating the impact of tail effects.