Context-based anomaly tracking represents a new approach to security enhancement of communication streams. By creating a system that develops an understanding of normal and abnormal based on communication history, it is possible to detect fluctuations in an evolving social network. Although more research is necessary to overcome current obstacles, the combination of social network analysis and anomaly detection techniques yields a promising set of applications for enhancing communication security. In this paper we will describe a system for context-based anomaly detection and then describe experiments for message surveillance application.