ATHITD: Attention-based temporal heterogeneous graph neural network for insider threat detection

Insider threats can lead to data leakage and system crashes within an organization, seriously compromising the security of information systems. Most existing detection methods focus on analyzing user behavior sequences or constructing user relationship networks based on behavior feature similarities between users to uncover malicious insiders. However, these methods ignore the association between users and entities (e.g., files, processes, PCs, websites, and removable devices) and the evolution of user behavior patterns over time. This paper proposes an attention-based temporal heterogeneous graph neural network for insider threat detection (ATHITD) to address these issues. Firstly, ATHITD constructs sequences of temporal heterogeneous graphs from various logs based on the specified time window to depict the evolving and complex relationships between users and entities. Secondly, it introduces temporal neighbors for target nodes within each time window to describe short-term temporal dependencies. Temporal neighbors are nodes identical to the target nodes and appeared in the previous time windows. It then employs the attention mechanism to learn the spatial heterogeneity of target nodes and the short-term feature evolution from temporal neighbors to target nodes. Additionally, it uses the self-attention mechanism in Transformer to learn the long-term feature evolution of user nodes across various time windows. Furthermore, ATHITD can focus on the time windows in which malicious activities occur, helping security personnel analyze potential malicious activities in the highlighted time windows. Extensive experiments on the public datasets CERT and LANL demonstrate that the long and short-term spatio-temporal node embeddings learned by ATHITD can be effectively used to identify malicious insiders. ATHITD achieves F1 scores of 0.96 and 0.97 on the CERT and LANL datasets, respectively, outperforming existing state-of-the-art methods.