Well known is the use of Iptables (read here) with Linux as a secure and effective firewall for your network connections, to customize and regulate all incoming, forwarded, and outgoing network traffic, and as a router or gateway for an internal LAN (Local Area Network). In addition to these and many more functions, Iptables can also be used to mangle, modify or alter parameters within the IP Header of a given Network Packet when necessary. The packets can be mangled in the built-in chains of PREROUTING (altering incoming packets prior to routing), INPUT (for packets coming into the box itself), FORWARD (for altering packets being routed through the box), and OUTPUT (for altering locally-generated packets before routing) and POSTROUTING (for altering packets as they are about to go out).
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Linux today is the fastest growing operating system that is replacing it’s competitors in almost every sphere of technology field. The major reason for this is the simplicity and robustness of this operating system. Besides, there is another quality in Linux that makes it favourite of many. This quality is the seamless customization that can be done with every aspect of this OS. One of the very important aspect is the Linux security. There are many protections and inbuilt security mechanisms that Linux incorporates in the name of system and network security. One of the inbuilt security mechanism is the Linux firewall. Linux provides a very flexible and powerful mechanism to customize the firewall. This mechanism is the Linux IPtables.
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