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I bought a USB 3.0 flash drive with a write protection switch for use with a Linux live distribution. My question is, once the OS is installed and running, I tested it and I can still install programs and make other changes to the OS while the write protection switch is on. Shouldn't that make everything read only?

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    The first thing to do is verify that your installation and changes are persistent and not just within the running RAM drive. Do this by shutting down completely then restarting, then check if your previous changes are still there. – user10216038 Mar 2 '20 at 4:13
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    You might not be making changes to the USB drive but to the OS running in memory – schroeder Mar 2 '20 at 7:37
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Assuming you really mean a USB flash drive, well, it's up to the firmware running on the device itself to actually implement that functionality. And since these sticks are definitely at the very least end of profit margin, I wouldn't be surprised at all if there's plenty devices that have some slider that doesn't do anything.

If you're actually referring to an SD Card (or similar) in a USB 3.0 flash card reader: That small tab on the side doesn't actually do anything, but drivers are asked to please kindly pay some respect to the fact that the user shifted that plastic thing by 2mm and kindly refrain from writing to the card. So, no wonder your PC ignores it: many modern readers don't even come with sensor for the position of that tab anymore.


What's the information security content of this answer? Simple: Especially in the world of least-cost consumer electronics (but sadly, also in the world of server/datacenter hardware), it's often not a good idea to trust protection mechanisms that aren't enforced by yourself, but by some black box that the supplier hands you.

The "Windows bitlocker depended on hard drive hardware encryption if available; hard-drives signalled ability to encrypt, but then, really, didn't encrypt" is an example of that. The occassional "oh, there's a clearly intentional backdoor in this (insert market leader here)'s {VPN/firewall/email scanner/IDS}" is another example.

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  • Bitlocker does not and never did depend upon hard drive hardware encryption! – user10216038 Mar 2 '20 at 0:44
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    @user10216038 oh yes, it does Microsoft says; also see this article. – Marcus Müller Mar 2 '20 at 8:59
  • Interesting! I knew drive hardware encryption was severely flawed but all of the Bitlocker I've dealt with has been software encryption. I wasn't aware of this odd interaction between the two. Thanks! – user10216038 Mar 2 '20 at 15:33

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