The protect button is used to lock important settings, such as network settings (IP, port, etc.) and adminstrator login credentials.
Once a setting has been protected, it can only be changed after a hardware reset using the "reset to defaults" pushbutton.
You can also use the protect button to prevent firmware updates.
Use this feature carefully. To un-protect, you will need physical access to the power controller reset switch.
Cycling power does not affect protection settings.