[throwaway09223]

> "No it’s not, my home networks "

When your phone is on 5g it is not behind a strong firewall, or any firewall at all. It's sitting directly on the internet. I can run a webserver on my phone and you can browse it.

> Do you not see the problem with all of my families devices “preferring” a neighbors network over mine?

If you've been laboring under the misconception that your phone is safe on your home network then perhaps this is a shock. But having your phone connected to a carrier means the carrier is responsible for providing a network.

Normally your phone is connected both to the carrier network and to whatever wifi network the user prefers, if wifi is available.

It seems like the major usability problem here is that instead of connecting to both networks, the carrier network supplants the user's network -- which breaks expectations when near user-run wifi.

[lxgr]

> When your phone is on 5g it is not behind a strong firewall, or any firewall at all.

I‘d be surprised if that’s true for most operators.

And even if there really is no stateful firewall: On IPv4 you’ll be behind carrier-grade NAT (so no inbound connections), and on IPv6 (including NAT64/DNS64), successfully guessing somebody‘s IP address seems extremely unlikely. (A server that you’ve visited might "dial you back", though.)

And for most users, the most visible effect will probably be that they can’t connect to their Chromecast, smart speakers, AirPrint etc, not decreased security.

[throwaway09223]

> I‘d be surprised if that’s true for most operators.

It's true for the operators I've tested so far

> On IPv4 you’ll be behind carrier-grade NAT (so no inbound connections)

Sometimes, but often still not the case.

> on IPv6 (including NAT64/DNS64), successfully guessing somebody‘s IP address seems extremely unlikely

Guessing a specific person's ip is a very different threat model from being hit by a random scan.