In an era of cooperating ad hoc networks and pervasive wireless connectivity, we are becoming more vulnerable to malicious attacks. Many of these attacks are silent in nature and cannot be detected by the conventional intrusion detection system (IDS) methods such as traffic monitoring, port scanning, or protocol violations. These sophisticated attacks operate under the threshold boundaries during an intrusion attempt and can only be identified by profiling the complete system activity in relation to a normal behavior. In this paper we discuss a hidden Markov model (HMM) strategy for intrusion detection using a multivariate Gaussian model for observations that are then used to predict an attack that exists in a form of a hidden state. This model is comprised of a self-organizing network for event clustering, an observation classifier, a drift detector, a profile estimator, a Gaussian mixture model (GMM) accelerator, and an HMM engine. We use this method to predict the intrusion sta...