>If the attacker has total control, then all bets are off no matter what mechanisms you put in first.

Great, so we now agree that it's important to keep the system patched and up to date.

That depends on updates never introducing new vulnerabilities.

I didn't say otherwise. Only that a forced update mechanism is insufficient for stakes as high as burning down the house. Maybe the patch fails to download/install, or they take too long to develop the patch in the first place, or the patch doesn't work for all models on the first try. There needs to be a simple kill switch if we're talking about threats like this.

Besides that, the safe mode oven should still be able to cook food manually.

Just as smart people agree that the manufacturer knows nothing about the situation at the appliance, and a forced update mechanism a la the first iteration of Windows forced updated ("update's here, restarting, too bad you're currently doing important stuff that won't be saved") is a stupid idea and outside of private use often a non-starter. That kind of condescension is generally only something you can do to private tech users.

Though I guess making the experience frustrating could keep more people from needlessly connecting everything to the network because it sound futuristic...

> If the attacker has total control, then all bets are off no matter what mechanisms you put in first.

You could have a second SoC on the device running off ROM, whose only purpose is handling this safe mode and controlling internet access of the main device. Keep it simple and make it essentially just a fuse that can be blown (turning off internet access) by a signed message from the manufacturer. Keep the hardware capability of this SoC to just that, so even if you have a vulnerability on that thing itself, an attacker can't really do anything with it. Keep the code running on that SoC simple and preferably make it a FSM that is proven to be free of vulnerabilities. Also make sure the main device can't interfere with it in any way.

Once the fuse is blown, the user needs to press a physical button on the device to re-enable internet access. Preferably ship the devices with this internet access disabled by default.

Even better yet, don't build an internet connected oven... but that ship has sailed in many areas.

Ideally yeah, the bar for critical appliances would be high enough for this. If not, disabling IP at the OS level would still be pretty good.