Automated processing, analysis, and generation of source code are among the key activities in software and system life-cycle. To this end, while deep learning (DL) exhibits a certain level of capability in handling these tasks, the current state-of-the-art DL models still suffer from non-robust issues and can be easily fooled by adversarial attacks.
Different from adversarial attacks for image, audio, andnatural languages, the structured nature of programming languages brings new challenges. In this paper, we propose a Metropolis-Hastings sampling-based identifier renaming technique, named Metropolis-Hastings Modifier (MHM), which generates adversarial examples for DL models specialized for source code processing. Our in-depth evaluation on a functionality classification benchmark demonstrates the effectiveness of MHM in generating adversarial examples of source code. The higher robustness and performance enhanced through our adversarial training with MHM further confirms the usefulness of DL models-based method for future fully automated source code processing.