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Changing port numbers

Hi Luis,
How can I go about changing port numbers or reconfiguring them? We are attempting to create a firewall with another computer to provide security for files kept on the one linked to it from the demons of the Internet.

Thank you for you help.
Dear Jose,

You begin the "changing port numbers" process by editing the "services" file: On a Win2k/NT server, this file exists in the %systemroot%\system32\drivers\etc\ folder; on a UNIX//Linux server, this file exists in the \etc\ directory. It's important that you understand that network security begins before your firewall; it starts with your border router and the implementation of an access control list (ACL). For example, your perimeter router should be configured to allow only the ports that you have set up in your firewall policy. (Keep in mind that any client workstation that plans to access your changed ports will need their local service file changed to reflect your ports.) In addition to changing ports and using ACL on your border router, you need to shut down all unused services in your router, your firewall, and your servers. Review the services you are running and apply the appropriate security hotfixes.

If you want to transfer files between two firewalls in a secure tunnel - one option is to set up VPN.

For a sample router configuration file, check out my articles in the Weakest Link series section.

Let me know if this provided the information you were seeking.

Thank you for submitting your question.
Luis

This was last published in July 2002

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