Thursday, August 13, 2015

USB Write-Blocking with the registry: Beware of UASP on Windows 8/8.1 - Workaround

I read once more the description of USB Attached SCSI on Wikipedia and I noticed these two lines:

Microsoft added native support for UAS to Windows 8. Drives supporting UAS load Uaspstor.sys instead of the older Usbstor.sys. Windows 8 supports UAS by default over USB 2.0 as well.

That explains why my UASP device works in "UASP" mode even if I plug it in on a USB 2.0 port.

I then thought: what if I replace uaspstor.sys with usbstor.sys?

And you know what? It worked!



These are the steps for the workaround:

  • boot into safe mode: within Windows, hold the SHIFT key and click Restart
  • click on the Troubleshoot button
  • select  Advanced Options
  • choose Command Prompt
  • login into your admin account
  • from command prompt, type C: and press Enter
  • type cd windows\system32\drivers and press Enter
  • type ren uaspstor.sys uaspstor.sys.old and press Enter to rename the file uaspstor.sys into uaspstor.sys.old (or whatever you like)
  • type copy usbstor.sys uaspstor.sys and press Enter to have an additional copy of usbstor.sys renamed into uaspstor.sys
  • close your command prompt by clicking on the "X" in the upper right corner
  • click on the Continue button to exit and reboot into Windows 8/8.1

Set "WriteProtect" to "1" in the registry, plug in your UASP device and finally enjoy it in read-only mode!

Since I applied the workaround, I haven't had any BSOD or software issue. So far it appears to be a stable workaround.

Your feedback is appreciated, thanks.

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