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[Polite explanation] How to use Linux firewall iptables

There are many things you would like to set up a firewall on Linux, too.Rather, because it is used as a server in a company, it is a place I want to be more careful about than a personal computer.This page tells about iptables to set up firewall on Linux. 

What is a firewall?

In general it means “fire wall”. It is analogous to shutting off fire from fire and preventing spreading fire.

In the context of computer networks, it is installed between the host itself and the network and the network to block unauthorized packets and improve security.

The most common example is Windows Firewall and packet filters built into routers.

This time we will introduce iptables packet filter which is commonly used in Linux.

What is iptables?

iptables is a general packet filter installed in Linux.

A packet is data that flows over a network, as it often comes from smart phone packet communication costs. The packet filter means that this packet is sorted out to separate what is passed and what is not.

iptables is a very high performance and high performance packet filter comparable to commercial products. Thank you for using it for free.

Since it supports not only the server itself but also packet transfer etc, it can be used as a network type firewall by operating on a machine with two network adapters and controlling packet transfer.

When combined with Snort etc., it can be used as UTM (integrated threat management system). It also has a stateful function to grasp the state of the packet and a log function.

Although it became difficult somewhat, this page explains the foundation of iptables.

iptables setting confirmation and explanation

Normally, when iptables command is executed, it is automatically loaded and made usable.

To display the filter rule that applied the setting, type the following command. When executed with the “-L” option, the currently set policy and a list of these rules are displayed.

The subsequent work should be done with root authority.

iptables -L

You should see something like the one below.

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