This book teaches readers how to use network security monitoring (NSM) to add a robust layer of protection around their networks. It covers deploying, building, and running an NSM operation using open source software and vendor-neutral tools, and shows how to interpret network evidence from server-side and client-side intrusions. Readers will learn how to determine where to deploy NSM platforms, deploy stand-alone or distributed NSM installations, use command line and graphical packet analysis tools, and integrate threat intelligence into NSM software to identify sophisticated adversaries. The book provides a comprehensive guide to building a security net to detect, contain, and control attacks, and is suitable for readers with no prior experience.