Linux Firewall

What is Firewall?
Firewall is a system of hardware or software designed to prevent some unauthorized Internet access from a private network prohibited by the security policy. It is  generally used to protect data from one network from users from other network connected to Internet. An enterprise connected to intranet uses firewall to protect its own data and also controlling the outside data its own users have to access to. Firewall acts as a gateway through which all messages entering and leaving the intranet pass through it and it examines all of them and blocks some specific ones that don't meet the security criteria. The two most common types of firewalls depending on the communication network are packet filtering firewall and proxy firewall. Packet filtering firewall examines each packet entering or leaving the network and then accepts or rejects on the basis of user defined rules. Proxy firewalls intercept connection networks through one port and later can forward or reject by using a set of rules. As far as firewall software is concerned these are programs installed in the operating system that intercept outside attacks before the system can even recognize them. 

Why Linux Firewall?
Linux is one of the most widely used operating system or software that any one can use, modify and redistribute without any restriction. Linux firewall are software based on Linux operating system use to secure the network. It  is very easy and secure enough to use on the internet and needs no external firewall. However, when one uses any windows machine, remote service or works on a personal server then external firewall becomes necessary. Again if you connect to the internet using a modem then there is no need to worry about the firewall as each time you are assign to a new IP address by your ISP. But if you connect to the internet by using a cable modem or DSL line then firewall becomes relevant as you are going to use the same IP address for a long period of time.  Linux firewall is the best option as the help of Linux firewall system both act as a web or e-mail server. Again you can control or determine the level of use of Internet. Linux firewall also provides web interface to control security on Linux server or even can block an IP or network completely. In this way the strong security system of Linux firewall is more effective and flexible than other expensive firewall routers. 

How to choose Linux Firewall?
If you are using a single PC at home or running windows like 95/98 without any server software on it then there is little to worry about. But if your home system is a server then that can make you vulnerable and you can face any kind of risk at any point of time. For example windows 95/98 includes a personal web server that routinely installed as part of a system. Again Microsoft FrontPage software also installs a web server on your system and these server can bring risks of hacking your system. Therefore, one needs to use a firewall especially Linux firewall server that provides increase security by preventing your system from outsiders while you are using Internet. However, there a variety of Linux firewalls available and choosing the best one according to your requirements is essential. The most common things that one should look are your technical objectives, the amount of traffic a particular firewall can process, and the effective traffic infection technology according the requirements. 

Linux Firewalls:
Following are the Linux based Firewalls that you can download install and use for securing your networks. 

1. Astaro Security Linux
   Astaro Security Linux is a new firewall solution: It distasteful inspection packet filtering, content filtering, virus scanning, VPN with IPSec and much more. With the web-based management tool and the ability to pull updates over the Internet it it is pretty easy to manage.
        
2. CensorNet
   CensorNet is Linux based Internet Management software designed to control and monitor individuals accessing Internet resources on a local area network. CensorNetT is the open source alternative to Web Sense, Surf Control, I-Gear, N2H2 and other commercial Internet management solutions. 
     
3. ClarkConnect Broadband Gateway
   ClarkConnect is a software package that transforms standard PC hardware into a dedicated broadband gateway and easy-to-use server. The software is a great solution for businesses, organizations, home offices, and networked homes.
     
4. Devil-Linux
   Devil-Linux is a mini distribution especially designed for a firewall and promises easy customization. Devil-Linux Boots from CD so there is no need for a hard disk. It supports Intel 486 and higher processors and uses the latest Linux kernel.
     
5. Mandrake Security MNF
   This integrated network security solution, Multi Network Firewall (MNF), combines firewall, Virtual Private Network (VPN), intrusion detection, and traffic management functions into an easy-to-use product.
     
6. Securepoint
   Through the spreading of hacker tools in the Internet it is already possible for unexperienced users to intrude in companies. Securepoint Firewall Systems fend off attacks on the company's network and thus offer an important protection against unauthorized access.
     
7. Sentry Firewall
   Sentry Firewall CD-ROM is a Linux-based bootable CDROM suitable for use as an inexpensive and easy to maintain firewall, server, or IDS(Intrusion Detection System) Node. 
     
8. SmoothWall GPL
   The SmoothWall project was founded by Lawrence Manning, Richard Morrell, Jon Fautley and Tom Ellis in Summer 2000, with the first version - version 0.9 - released via the Sourceforge open source collaboration site in August of that year.
         
9. Immunix Secure Server OS
   Immunix OS is a Linux distribution designed to be secure both now and in the future. The Immunix security tools (Stack Guard T, SubDomainT, and CryptoMarkT)provide security bug tolerance so that even if security vulnerability is found in one of the programs supplied with Immunix, the vulnerability will probably not be exploitable by attackers.
            
10. Luinux
    Luinux is an Internet Gateway for your home network equipment (PC, VideoConsole, TV, oven, ...). Luinux comes preconfigured so, ideally, you just have to install it and play.