To change the WAN firewall for your Netcomm modem, follow these easy steps.

1. First, you'll need to log in to your Netcomm router.
2. Once you're logged in, click on Advanced Setup in the left-hand bar, and then click on WAN Service. You'll see this screen:
   
3. You'll see the Wide Area Network (WAN) Service Setup screen. At the far right of the screen, you'll see an Edit button - click it.
4. Below the MTU Size settings, you'll see a checkbox to enable/disable the firewall for your router.
   
5. Click on the box to ensure it's ticked (which means the firewall is enabled).
6. Once you've done this, click on the Apply/Save button, and that's it - you're done!