介绍了防火墙的基本概念及其主要功能,分析了Linux 内核防火墙Netfilter 的架构、构建防火墙的工作原理及其与内核的交互.最后给出了Netfilter 构建防火墙的一个实例。 关键词:防火墙 Linux Netfilter 包过滤 Abstract:The basic concept and most functions of firewall were introduced here.It analysed the frame of netfilter,explained how to interact between kernel.Finally,a case study of using netfilter as a firewall was given. Key words:firewall;Linux; Netfilter;packet filtering