Financial fraud detection is critical for market transparency and regulatory compliance. Existing methods often ignore the temporal patterns in financial data, which are essential for understanding dynamic financial behaviors and detecting fraud. Moreover, they also treat companies as independent entities, overlooking the valuable interrelationships. To address these issues, we propose ACRF-RNN, a Recurrent Neural Network (RNN) with Attention-based Conditional Random Field (CRF) for fraud detection. Specifically, we use an RNN with a sliding window to capture temporal dependencies from historical data, and an attention-based CRF feature transformer to model inter-company relationships. This transforms raw financial data into optimized features, fed into a multi-layer perceptron for classification. Besides, we also use the focal loss to alleviate the class imbalance problem caused by rare fraudulent cases. This work presents a novel real-world dataset to evaluate the performance of ACRF-RNN. Extensive experiments show that ACRF-RNN outperforms the state-of-the-art methods by 15.28% in KS and 4.04% in Recall. Data and code are available at: https://github.com/XNetLab/ACRF-RNN.git.

Tabular data is prevalent in many fields. In practice, tabular data classification may encounter severe challenges due to class imbalance, i.e., some majority classes overwhelm minority ones. Such imbalance could lead to biased prediction tendency of trained classifiers towards majority classes. Oversampling minority classes is an essential solution due to its generality and independence of downstream tasks. Recent years have witnessed the advantages of generative adversarial networks (GANs) in synthetic data generation, favored for their ability to generate quasi-realistic samples. However, challenges arise when the size of minority classes is too small to provide sufficient information for learning real data distributions. Furthermore, the generated minority-class samples could exacerbate the class overlap problem, i.e., some generated samples unexpectedly overlap with partial majority-class samples. To address these challenges, this paper presents B2BGAN, a novel GAN-based approach for oversampling imbalanced tabular data. To capture the real data distribution in a fine-grained manner, we propose a novel backbone-to-branches neural network for the generator to fit the majority and minority classes simultaneously. The backbone network fits the whole distribution of the entire data, while each branch network grasps the distinctive characteristics of individual classes. To alleviate the class overlap problem of generated samples, we develop a prototype-guided loss function to ensure that generated samples are closer to the corresponding class prototypes. We evaluate the effectiveness of B2BGAN on six real-world datasets using six metrics. Experimental results demonstrate that our method outperforms state-of-the-art models by 5.38% in AUC and 10.19% in AP.