Deep Neural Embedding for Software Vulnerability Discovery: Comparison and Optimization

Due to multitudinous vulnerabilities in sophisticated software programs, the detection performance of existing approaches requires further improvement. Multiple vulnerability detection approaches have been proposed to aid code inspection. Among them, there is a line of approaches that apply deep learning (DL) techniques and achieve promising results. This paper attempts to utilize CodeBERT which is a deep contextualized model as an embedding solution to facilitate the detection of vulnerabilities in C open-source projects. The application of CodeBERT for code analysis allows the rich and latent patterns within software code to be revealed, having the potential to facilitate various downstream tasks such as the detection of software vulnerability. CodeBERT inherits the architecture of BERT, providing a stacked encoder of transformer in a bidirectional structure. This facilitates the learning of vulnerable code patterns which requires long-range dependency analysis. Additionally, the multihead attention mechanism of transformer enables multiple key variables of a data flow to be focused, which is crucial for analyzing and tracing potentially vulnerable data flaws, eventually, resulting in optimized detection performance. To evaluate the effectiveness of the proposed CodeBERT-based embedding solution, four mainstream-embedding methods are compared for generating software code embeddings, including Word2Vec, GloVe, and FastText. Experimental results show that CodeBERT-based embedding outperforms other embedding models on the downstream vulnerability detection tasks. To further boost performance, we proposed to include synthetic vulnerable functions and perform synthetic and real-world data fine tuning to facilitate the model learning of C-related vulnerable code patterns. Meanwhile, we explored the suitable configuration of CodeBERT. The evaluation results show that the model with new parameters outperform some state-of-the-art detection methods in our dataset.