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A security risk with ordinary flash drives is that they have re-writable (flashble) firmware, which basically lets a hacker replace the operating system of the USB drive with their own.

Are there any USB drives that are guaranteed to be read-only and do not allow their firmware to be re-flashed?

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  • I thought there are very less USB drives which have writable firmware.
    – defalt
    Nov 5, 2017 at 7:21
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    Is it acceptable to have firmware which is write-able, but only if you push a physical button with a paper clip otherwise the firmware is inaccessible. Even then a button push is only good for something like 5 minutes.
    – cybernard
    Dec 29, 2017 at 22:48
  • @cybernard yes, if the firmware is read only in a way that is physically controllable, then that is good enough.
    – Tyler Durden
    Dec 29, 2017 at 23:44
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    @TylerDurden Did you ever find a UFD with read-only firmware?
    – user186877
    Oct 12, 2020 at 16:18

2 Answers 2

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Yes: https://www.kanguru.com/storage-accessories/kanguru-flashtrust-secure-firmware.shtml

There exist a few other, mostly encrypted devices uses secure firmware, but this is one unencrypted drive that uses secure firmware with signed firmwares.

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  • As far as I could tell, this does not have read-only firmware. Just like every other USB flash drive, it has flashable firmware. It has a write-protect switch, but that prevents anything from being written to the drive at all. I want to be able to write to the drive. I just don't want the firmware to be writable or flashable.
    – Tyler Durden
    Nov 5, 2017 at 18:38
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    @TylerDurden If you read the description, you will see that the firmware is signed with RSA2048, and the drive will only accept firmware updates signed by the manufacturer. Thats much more secure than a non-updateable drive, as the non-updateable drive could have exploits which cannot be fixed, which FlashTrust can fix after release. The firmware security is present regardless of the position of the write protect switch.
    – sebastian nielsen
    Nov 5, 2017 at 18:43
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    “Code signing comes with the same issue: Any bug anywhere in the controller code would allow you to circumvent the code signing,” Karsten Nohl said. “Much more effective—and easier to implement—is preventing firmware updates entirely using a hardware fuse (or software fuse for the interim as a somewhat effective stopgap).”
    – user186877
    Oct 12, 2020 at 16:14
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    Also, when the drive has its switch in the read-only position, it will also block ANY firmware updates, regardless of signature. In its read-write position, it will only accept SIGNED firmware updates. Note that the signature is verified in the boot code, NOT in the firmware update code, meaning that the drive will refuse to load an firmware file with a invalid signature, even if you would physically flash the firmware image to the actual flash chip (by desoldering it and flashing in the image from the outside).
    – sebastian nielsen
    Apr 14, 2021 at 4:38
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http://www.isostick.com https://www.amazon.com/Elegant-Invention-isostick-revC-isostick/dp/B008S4XY08/ref=sr_1_1?ie=UTF8&qid=1514598410&sr=8-1&keywords=isostick

I submit the ISO stick as a candidate for consideration. It is in a USB factor, and you plug an SD card into it for storage. From the computer side it is just a flash drive. This is done so even if the device stops working or gets crushed you can get the SD card out and save your otherwise doomed data.

The firmware is flashable, but only through the use of a physical button. The button is at the bottom of a hole which is only big enough for the tip of a paper clip. It is impossible to accidentally push. Additional, I believe the timeout is short like 5 minutes, after you push the button to flash the firmware or it becomes unreachable again. During the 5 minute interval an additional port is visible which allows the firmware to be flashed.

In addition, it has a second read-only switch to make the USB storage if you choose to use it. Read-only ON plug it into a machine with a virus, and the virus can't touch it.

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  • Are you absolutely sure that it is only flashable when you use that button? For example, can it not be modified by writing to a specific, high address as it can for many other drives?
    – forest
    Dec 30, 2017 at 3:45
  • I know it is supposed to work that way, but lack the software and knowledge to put it to a live fire test.
    – cybernard
    Dec 30, 2017 at 3:52

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