Spoofing occurs when someone attempts to access your system by pretending to be within a system that you normally trust within your own network. You need to protect any interfaces that are linked to a public network from this type of attack.
You can protect against spoofing by completing the Spoof Protection wizard that is available from the Packet Rules Editor in IBM® Navigator for i. This wizard helps you to assign rules to your vulnerable interfaces. After the rules are active, a system from the public (untrusted) network is not able to act as a trusted workstation from a private (trusted) network.