In most organisations, network security has become interwoven with standard network and system administration. Threats in the form of malicious hackers, self-propagating worms, denial of service attacks, and other nefarious security problems loom large for administrators. . . .
In most organisations, network security has become interwoven with standard network and system administration. Threats in the form of malicious hackers, self-propagating worms, denial of service attacks, and other nefarious security problems loom large for administrators.

Of course, one of the building blocks of network security is a good firewall. Although many companies pay top dollar for commercial firewall solutions, Linux has long been a popular option for those who want to save some big money and who don't mind rolling up their sleeves and building the firewall configuration themselves.

Fortunately, the Linux firewall solution has continued to improve and the netfilter/iptables system now provides a robust and supremely flexible solution. netfilter/iptables(netfilter is the name of the project, and iptables is the name of the Linux software itself) is a system integrated into the Linux 2.4.x kernel for the handling of packet filtering. It is the successor to the ipchains and ipfwadm systems and is the first to be incorporated directly into the kernel. Here's a look at how you can build a strong Linux firewall with iptables.

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