The Internet has been used in various types of devices like laptop, desktop, smartphones, household equipment, sensors, Internet of Things etc. So it becomes the essential part of our daily life. As a connectivity of the network increases day by day, there are a lot of network security threats in our daily life. In recent years, all kinds of security attacks break out continuously such as in Russia there were over 100 user accounts were hacked, Dailymotion sites data were hacked 85.2 email addresses extracted, Myspace data hacked, a malicious attack on the Reserve Bank of India [1]. That’s why it has become extremely important to protect our server or web assets. How should we proceed to establish a secure environment? There are many ways to ensure the security of your dedicated server, we will discuss firewalls their usage and configuration and which may be best for a different application.

LINUX FIREWALL A

firewall is an important tool that protects itself and other hosts on a network from an attacker on untrusted network[2]. A firewall can be very beneficial if it was used as a filter towards all of the Internet access to and from the system passes through it. A firewall system can also be configured to conceal multiple hosts behind a single Internet protocol address using a process known as Network Address Translation. The firewall protected server’s schema as shown in figure 1.

II. KEY TECHNOLOGY

A. NETFILTER

Netfilter is a packet filtering framework provided by the Linux kernel which allows different networking related operations to be implemented in the form of customized handlers[3][4]. It gives different functions and operations for network address translation, packet filtering, and port translation. It serves the functionality that is needed for guiding packets over a network likewise for serving a capacity to block the packets from reaching sensitive location with a computer network.