This is my sixth edition to my series "Networking Simplified." I know
these are normally short, but concise. I want everyone to be able to
browse them for information, rather than have to skip back and forth to
read about one thing at once. In this tutorial, i will go over the basics
of firewalls. Different kinds of firewalls, and what they are used for.


A firewall is really a group of programs, working from the gateway of your
entire network. The gateway is the place where you connect to the
internet. I will go into gateways and proxies etc in a later edition. It
protects the resources of a private network from the users of other
private networks. This term is normally interchangeable with security
policy, because what a firewall does is set up what you do and do not
allow access. An intranet lets users access the actual internet, by
installing a firewall to prevent outsiders from getting in to see their
own private information. It just controls what the users have access to.
For example certain ports, such as telnet port 23, or ssh port 22.

Firewalls work with routers that checks over packets to see if they are
forwardable or not. If the packets are poisoned, generally the firewall
will not allow them through unless you have specified a certain poisoned
packets access granted. A certain type that is. A firewall can include a
proxy server, like i said i will go over proxies later on.

Firewalls can be screened by allowing domain names or IP addresses.
However, some firewalls allow remote access, which means you can gain
access from a different network with the proper authentication. For
example ssh'ing into the ssh server of the network. Alot of firewalls
feature log capabilities, and even feedback of live attempts to gain
access. Some are graphical while others are console based.

I will now go over a few examples of firewalls that you may use for free.


Tiny Personal Firewall -

This is a good, easy to use firewall that works only for windows.

The tiny firewall has special capabilities of signature based intrusion
detection, bi-directional stateful packet inspection desktop firewall etc,
and prevents mass deployment of .msi packages.

Windows, imo, offers only good firewalls for a fee. As usual. The tiny
personal firewall download above is only a trial version, but the best i
would recommened out of the four main used windows ones:


zone alarm


and of course, tiny.


Unix Firewalls.

Most unix systems, such as linux, have what are called IP Masquerading,
built in. THis allows you to use a NAT router AND a firewall for your
network. imo, firewalls aren't necessary on most *nix platforms with
iptables and ip masquerading. So i won't go over those here. Since windows
has a problem with security, thats the reason i actually spoke of brand
name ones there.


Hope you enjoyed this version of "Networking Simplified." Firewalls are
great tools for the system administrator and the end user alike. is recommended by me for windows, mac, and linux