After you establish the basic security function of i5/OS, it's time to implement a firewall.
A firewall is a combination of hardware and software that controls access between your system and the Internet. While technically it is not necessary to install a firewall to connect to the Internet, you would be foolish to go without one. It's like driving a car without wearing a seatbelt. You don't need it until something bad happens, and when it does, a seat belt can save your life.
Here are the benefits of a firewall:
Control access to your system.
Concentrate and simplify security administration.
Protect services, such as network file systems.
Improve system availability by blocking denial of service attacks.
Provide statistics of network use and attempted misuse.
If you don't already have one, you should consider a PC firewall product. You want your firewall separated from your main processing. This can be a firewall on a stand-alone server, or possibly a firewall running on a separate iSeries partition using either AIX or Linux.
The typical configuration is a dedicated Web server and a firewall to protect the internal network