Security Information and Review

Collection of security information and review

Base Linux Security with IPTables

Author : Admin

Most people think that to protect computer networks from outside attacks by using firewall but they don’t understand what a firewall is and how it really work. A firewall inspects packets as they arrive on an interface, searching a table until it finds a matching rule to determine what is should do with each packet and the follow the action the rule specifies.

If the packet does not match a specific rule, a default action decides the packet’s fate, generally known as falling through the bottom of the rules. For firewalls, the generally accepted good default action is Deny. That is, unless we explicitly permit a particular access, the packet is dropped. This allows us to permit what we know and block what we do not.

A Linux server running a well configured firewall is one of the most effective ways to protect the local server and any internal networks behind it. The essential tools for the most common Linux Operating System are Netfilter / Iptables. Includes all the different flavors of Linux distributions such as Red Hat / Fedora Core, Debian, Ubuntu, Suse, CentOS, Gentoo, Linspire and others. This tools gives the administrator the flexibelity to define the type of traffice allowed in and out of the firewall.

The Netfilter / Iptables project started in 1998 and continues the work from the ipchains and ipfwadm projects that preceded it. Both ipchains and iptables were developed by Rusty Russell.

The actual kernel module that provides this functionality is netfilter while iptables is the user space program to adjust the rules used by netfilter to manipulate traffic. To create netfilter security policies, we must define tules that match on packet contents and define a target that specifies what to do with any packets that match the rule.

Obtaining netfilter depends on which Linux distribution we have. After installation, there should be an iptables ini script in our ini directory. Some Linux distributions add it to startup while others make we do it manually.

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Categories: Linux Security
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