摘要:隨著Internet的迅速發展，網絡越來越成為了人們日常生活不可或缺的一部分，而隨之引出的網絡安全問題也越來越突出，成為人們不得不關注的問題。

　　為了在一個不安全的網際環境中構造出一個相對安全的環境，保證子網環境下的計算機的安全運行免受到外部的侵害，針對當前的網絡問題，本文主要介紹了幾種流行的防火墻技術及其工作原理。在防火墻的基本概念、作用和基本類型的基礎上，重點分析了linux諸版本中所使用的基于包過濾型防火墻的工作原理，并在此基礎上對linux2.4版本出現的iptables技術作了詳細的構架環境分析以及實現，以此來測試和部署出一個較為安全的網絡環境，使得在一個不安全的網絡環境中有效防范外部網絡的攻擊行為，讓整個網絡具有較高的安全級別。

關鍵詞： 防火墻、網絡安全、Linux、包過濾技術、Iptables

Abstract:With the rapid development of Internet, the network is more and more become an integral part of People’s daily life, and subsequently leads to the problem of network security that has become increasingly prominent, as people have concerns.

　　　In order to construct a relatively safe environment in a secure environment, to ensure the subnet environment of computer security operation and not infringed by the external, in view of the current network problems, this paper mainly introduces several popular firewall technology and how it works. On the basis of the basic concept, role and basic types behind a firewall, we mainly analys its working principle,which is based on the working principle of packet filter firewall in each version of Linux,and based on that, we analyzed in detail and achieve the structure environment of iptables technology which appears in version 2.4 of Linux,and use it to test and deploy a safer network environment,which will make computers can effectively guard against external network attack behavior in an unsafe network environment, let whole network has a higher level of security. 

Key Words: firewall、Network Security、Linux、Packet filtering technology、Iptables