[bcook]

> And by the way, nobody, noone forbade you from having explicit firewall rules denying anything from anywhere, not explicitly allowed. Just like it is done in a proper IPv4 configuration.

Sure, in a perfect world, migrating to IPv6 should be safe, but the default configuration on many ISP-supplied routers has no firewalling beyond what NAT offers.

[Dagger2]

Which is nothing. NAT offers zero firewalling.

I won't say there aren't ISP routers without firewalling, but for the most part they're pretty decent at having it. It's just that the firewalling is a completely separate thing to NAT.