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Recent studies have shown the promise of using utility functions to detect anomalous behavior in software systems at runtime. However, it remains a challenge for software engineers to hand-craft a utility function that achieves both a high precision (i.e., few false alarms) and a high recall (i.e., few undetected faults). This paper describes a technique that uses genetic programming to automatically evolve a utility function for a specific system, set of resource usage metrics, and precision/recall preference. These metrics are computed using sensor values that monitor a variety of system resources (e.g., memory usage, processor usage, thread count). The technique allows users to specify the relative importance of precision and recall, and builds a utility function to meet those requirements. We evaluated the technique on the open source Jigsaw web server using ten resource usage metrics and five anomalous behaviors in the form of injected faults in the Jigsaw code and a security attack. To assess the effectiveness of the technique, the precision and recall of the evolved utility function was compared to that of a hand-crafted utility function that uses a simple thresholding scheme. The results show that the evolved function outperformed the hand-crafted function by 10 percent. |
