Many flash chips have write enable pins at the hardware level. So this support really does still exist in theory!

However, these pins mostly aren't used for any kind of switch in basically every PCB design I've seen. Either it's "always enabled" so the storage can always be written, or it's a chip that's programmed from the factory and always disabled to prevent any kind of user update.

I'd sure hate to have my system ransomware compromised, and when I try to restore from a backup drive, the ransomware encrypts it, too, as soon as I plug it in.

I also have, on occasion, flipped the from and to parts of the command to restore from a backup. I'd really like to have a hardware switch to make the drive read-only.

They exist, but only as very expensive specialty gear for digital forensic investigators.

https://digitalintelligence.com/store

> very expensive

Indeed, for a 2 cent switch.

These also exist for removable drives (not really any different price compared to normal drives, in wide use) in the govt/defense market, where using a hardware write switch when moving data between airgapped systems in a controlled way is common.

Why doesn't MS do similar on all of their OS code by placing it on a read-only filesystem? Only allow updates when reboot into an update mode.

I have zero faith in software read-only modes.

Android does this. OS is read only. Updates happen on second partition and takes effect by swapping partition on reboot. Integrity is verified by secure boot.

Interesting. How is it verified? Maybe keep Merkle tree hash of eveything in TPM?