[10000truths]

NAT doesn't imply stateful firewall at all. NAT is literally just rewriting IP addresses on incoming/outgoing packets. I could have a single machine behind a middlebox, and the middlebox could just rewrite the IP source/destination of egress/ingress packets, and that would be NAT - and I'd still be able to successfully receive incoming packets from the big bad web. In fact, you can do this without the middlebox using an iptables MASQUERADE rule.

But even then, the added security of a stateful firewall as provided by a router is dubious. You know what else has a "stateful firewall"? Your kernel's TCP/IP stack. It isn't gonna accept random connections from the Internet unless there is an application actively listening to a port and accepting packets. And I trust the Linux/NT/BSD kernel to be more secure with ensuring that than a binary firmware blob from a router manufacturer.

[kortilla]

Sorry, you’re very confused about the NAT that is widely deployed. It’s absolutely not 1:1 NAT because that buys effectively nothing from a scaling perspective.

> But even then, the added security of a stateful firewall as provided by a router is dubious. You know what else has a "stateful firewall"? Your kernel's TCP/IP stack. It isn't gonna accept random connections from the Internet unless there is an application actively listening to a port and accepting packets.

That’s the fucking problem. All kinds of vulnerable/misconfigured software just binds to 0.0.0.0:<whatever> and calls it good. My fridge does this, my washer does this, my TV does this. This is the world of IoT.

> And I trust the Linux/NT/BSD kernel to be more secure with ensuring that than a binary firmware blob from a router manufacturer

It’s not, it takes a single API call to have a program start listening because that’s the entire job of the kernel. You have to configure a firewall on top of it to make sure vulnerable software isn’t exposed to the internet.

[Dagger2]

The kind of NAT that's widely deployed doesn't act as a firewall though. It buys you nothing from a security perspective. It's entirely possible to connect inwards over a NATing router unless there's also an additional firewall configured.

Stateful NAT does imply state tracking, which is a major component needed to implement a stateful firewall, but it is not itself a stateful firewall.