This book is a guide on network security monitoring. The author begins by explaining some of the basics of computer networking and the basic tools which can be used for monitoring a computer network. The process of capturing and analyzing the packets of a network is discussed in detail. This is a good technique which can help network security experts identify anomalies or malicious attacks on the packets transmitted over a network. You are also guided on how to monitor the network traffic for the Heartbleed bug, which is very vulnerable to network attackers. Session data is very essential for network security monitoring. The author guides you on how to use the session data so as to monitor the security of your network. The various techniques which can be used for network intrusion detection and prevention are explored. You are also guided on how to use the Security Onion to monitor the security of your network. The various tools which can help in network security monitoring are discussed. The following topics are discussed in this book: - Network Monitoring Basics - Packet Analysis - Detecting the Heartbleed Bug - Session Data - Application Layer Metadata - URL Search - Intrusion Detection and Prevention - Security Onion