Does Amahi provide a firewall?
No, Amahi is not a router and it absolutely requires a separate firewall to be between the Amahi server's network and the Internet at large. Amahi is designed to be in a more-or-less trusted environment like a home network.
You should definitely have a separate firewall isolating your network from the Internet. Typically, the firewall is in your router/gatweay/modem. Your Amahi HDA should definitely not be reachable directly from the Internet (only if you did some port forwarding in your firewall).Back to the FAQ