All servers should be configured to block at least the unused ports, even if there are not a firewall server. This is required for more security. Imagine someone gains access to your firewall gateway server: if
your neighborhoods servers are not configured to block unused ports, this is a serious network risk. The same is true for local connections; unauthorized employees can gain access from the inside to your other
servers in this manner.
In our configuration we will give you three different examples that can help you to configure your firewall rules depending on the type of the server you want to protect and the placement of these servers on your
network architecture.
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The first example firewall rules file will be for a Web Server.
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The second for a Mail Server.
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The last for a Gateway Server that acts as proxy for the inside Wins, Workstations and Servers machines.
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See the graph below to get an idea:
The list above shows you the ports that I enable on the different servers by default in my firewall scripts file in this book. Depending on what services must be available in the server for the outside, you
must configure your firewall script file to allow the traffic on the specified ports.
www.openna.com is our Web Server,
mail.openna.com is our Mail Hub Server for all the internal network,
deep.openna.com is our Gateway Server
for all the examples explained later in this chapter.
