It is important for all to realize that information security is more than just strong passwords, policies or technologies. Information security is about developing and implementing a strategy for information security to protect technology resources. One such strategy to protect network resources is called defense in depth. The goal of a defense in depth strategy is to incorporate a wide array of information security tools to protect your company or network assets. Today one of the key components of a defense in depth strategy is a firewall. In simplest terms, a firewall is a piece of software or hardware or both that stands in front of your network protecting it from malicious threats that are present on the Internet. It performs these tasks by examining the flow of data into and out of your network. The firewall contains rules that determine what action to take based on the flow of packets. Several years ago, a firewall was considered adequate protection for protecting your network resources. However, today a firewall is part of a set of minimum requirements for using and operating on the Internet. Firewalls come in all different flavors and operating systems. This paper will examine and contrast three common types of public accessible Internet firewalls. The firewalls examined exist in the UNIX or Linux environment. This paper will neither consider Microsoft’s solution called Internet Security and Acceleration Server (ISA) nor any appliance or vendor specific firewalls, but will examine and contrast the foundation of many firewalls today. The publicly available firewall solutions offer a more flexible approach to network security. Often one can get away with implementing one of these firewalls without the acquisition of additional hardware. The three firewalls examined in this paper are ipfilters, ipchains and iptables.
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