介绍入侵检测的概念及系统构成,指出入侵检测系统能弥补防火墙的部分不足,为防火墙规则更新提供指导,堪称防火墙之后的第二道安全闸门,详细介绍电子科技大学图书馆网络安全系统中策略管理、协议筛选、策略调整的特点,并介绍网络入侵检测系统的实际应用。 This paper introduces the concept and system constitution of intrusion detection. It points out that intrusion detection system can make up for some shortages of firewall and provide guidance for firewall rule updating. It is called the second security gate after firewall, and details the strategy in UESTC library network security system Management, protocol screening, policy adjustment features, and introduce the actual application of network intrusion detection system.