An Introduction to Intrusion Detection.- The Base-Rate Fallacy and the Difficulty of Intrusion Detection.- Visualizing Intrusions: Watching the Webserver.- Combining a Bayesian Classifier with Visualization: Understanding the IDS.- Visualizing the Inner Workings of a Self Learning Classifier: Improving the Usability of Intrusion Detection Systems.- Visualization for Intrusion Detection-Hooking the Worm.- Epilogue.