Yes, "drop all" at the end of the firewall input chain (prevent any service to be discovered from ISP/Internet)
and change MAC address of interface where ISP is connected.

所有的人提问,不要修改or change firewall rules unless you know what you are doing!
Simply adding a block rule to your config, on the input chain, could easily lock yourself out of the router.
Ensure you have access as an admin in a higher up (in order) input chain rule