[drhagen]

I remember USB drives in the '00s that had a read-only toggle. They were useful for rescuing machines that had a virus.

Edit: A quick search reveals that, of course, you can still buy them today. I have not felt a need for one in ages.

[Hizonner]

I strongly suspect that most or all of the modern "hardware" write-protect switches are actually just suggestions to the drive firmware. Which may very well itself be modifiable.

[Gormo]

I can't imagine how it would be possible to do it any other way for a flash storage device.

A mechanical hard drive could at least theoretically have a physical lock attached to the drive head which prevents it from approaching the platters if it is engaged.

[commercialnix]

This is the way a smart person looks at write-protect switches.

[Terr_]

Hmmm, I would absolutely buy one of those if it also had a hardened case and a firm connection point for my real-world keychain. The use-case is a "my house burned down what next" backup, password-manager stuff and other details I might need before/without accessing any cloud-backup services.

I may need to read some of its files on a not-very trusted device, and I don't want to risk that device also tampering/trojan'ing other files, like backup copies of the software needed to decrypt the data files.

A simpler scenario might be a USB stick that I use for carrying files to be printed at the local library.

[GuB-42]

I have one of these as a boot disk (Medicat) for this exact reason.

Also because some of the software included in Medicat is flagged by some anti-virus software and I don't want them removed.