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4. Firewalling Software

4.1 Available packages

If all you want is a filtering firewall, you only need Linux and the basic networking packages. One package that might not come with your distribution is the IP Firewall Administration tool.

(IPFWADM) Comes from

If you want to setup a poxy server you will need one of these packages.

  1. SOCKS
  2. TIS Firewall Toolkit (FWTK)

4.2 The TIS Firewall Toolkit vs SOCKS

Trusted Information System ( has put out a collection of programs designed to facilitate firewalling. The programs do basically the same thing as the SOCKS package, but with a different design strategy. Where Socks has one program that covers all Internet transactions, TIS has provided one program for each utility that wishes to use the firewall.

To contrast the two, let's use the example of world wide web and Telnet access. With SOCKS, you set up one configuration file and one daemon. Through this file and daemon, both telnet and WWW are enabled, as well as any other service that you have not disabled.

With the TIS toolkit, you set up one daemon for each WWW and telnet, as well as configuration files for each. After you have done this, other internet access is still prohibited until explicitly set up. If a daemon for a specific utility has not been provided (like talk), there is a "plug-in" daemon, but it is neither as flexible, nor as easy to set up, as the other tools.

This might seem a minor, but it makes a major difference. SOCKS allows you to be sloppy. With a poorly set up SOCKS server, someone from the inside could gain more access to the internet than was originally intended. With the TIS toolkit, the people on the inside have only the access the system administrator wants them to have.

SOCKS is easier to set up, easier to compile and allows for greater flexibility. The TIS toolkit is more secure if you want to regulate the users inside the protected network. Both provide absolute protection from the outside.

I will cover the installation and setup of both.

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