How to Build a Firewall in Linux

Linux is considered a secure operating system, especially compared to Windows. As such, it is appropriate to use it as a firewall for your home or business network. However, configuring a firewall by hand can be a time-consuming and confusing process. Firewall Builder (fwbuilder) is a graphical-based tool that will configure a firewall based on iptables (netfilter), ipfilter, pf, ipfw, Cisco PIX (FWSM, ASA) and Cisco routers extended access lists. It can be installed and used on many different operating systems, including Linux, FreeBSD, OpenBSD, Windows and Mac OS X. Not only will it create a firewall for a local network, it can be used for a remote network also.

Difficulty: Easy

Instructions

Things You'll Need:

• fwbuilder

1. Install fwbuilder. Use your graphical package manager or command line tools.

2. 
    
   Firewall Builder

   Open fwbuilder. In GNOME, it will be found under "Administration ' System." In KDE, it will be found under "Start ' Internet."

3. 
    
   New Firewall

   Click on the icon to the left of the "user/standard" drop-down box and choose "New Firewall."

4. 
    
   Choose Name

   Fill in the appropriate information in the pop-up window. For the purposes of this article, I named the file "test," chose the iptables firewall software and set the OS to Linux.

5. Click the "Use preconfigured template firewall objects." You can always add and remove rules once everything is set up.

6. Click "Next" to go to the next screen.

7. 
    
   Choose type of firewall

   Choose your firewall type. Click through the options on the top-left side of the window. Each option has a different set of rules. For a single machine, you will probably choose "fwtemplate1," which is the option I chose for the example. It has unrestricted outbound access, but will only allow access to the firewall with ssh or the internal network.

8. Click "Finish" to complete your firewall setup.

9. 
    
   Review your firewall settings

   Review your firewall and add any additional rules by choosing "Rules ' Insert Rule."

10. Choose "Rules ' Compile" to compile your firewall.

11. Choose "Rules ' Install" to install the firewall.

References

• Firewall Builder Cookbook