Make a USB Read Only

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There are two ways to make a USB stick read only. One way is a universal solution and is 100% permanent, the other way is PC specific and a good deterrent. When we say 100% permanent, this means the USB stick is read only (write protected) on all computers, whether it be a Mac, PC, Linux, etc type computer, the USB is read only and the status cannot be changed. The other method flags a USB device to be read only in relationship to the PC it is connected to so that whenever that USB stick is connected to that computer, it makes the USB read only and blocks all write commands to the device.

Most times an IT manager or content owner wants the USB stick to be read only so the files cannot be deleted or formatted of the drive. Another reason for making a USB read only is for the original files to remain the same and blocks the ability for files to be changed or manipulated. Finally, it’s smart to have USBs read only so that virus’ don’t jump onto the drive and possibly spread to other computers.

Let us start with the less permanent way because it’s easier to do and doesn’t require any specific hardware. You will need at least a Windows 7 machine or higher. The Windows 7 machine will have DiskPart utility which allows us to perform all sorts of cool things to flash drives, like setting write protection.

Connect the USB to your Windows computer. To begin, go to your Windows Start and in the Search Field type “cmd”:

Make a USB Read Only

This will run your Command prompt.

  • Next, you will want to get to the C root of the Command prompt and if you are signed in as a user you can simply type cd\ this will get you back to the root of the C drive.
  • Type LIST DISK
  • Now you will need to find the USB stick connected to your PC. Most likely it’s DISK 1
  • We must select the device we want to change the attributes for, so type SELECT DISK 1
  • To set the drive as read only, type ATTRIBUTES DISK SET READONLY
  • DiskPart will confirm the attribute was sent and you can now type EXIT

Make a USB Read Only

So what we did is make a registry entry in that Windows machine to always treat that flash drive as read only. As you can see this is a simple solution that is PC specific. In addition, if you get a registry cleaning tool like “USB Scrub” that utility will remove the registry entry we just made and the User can once again do anything they want to the drive.

Read-only file (NTFS)

Another nice and easy function to make a file more permanent is to set a file as Read Only. When a file on the USB stick is set to Read Only it blocks the user from deleting or formatting the drive. However, this only works on the PC so if the USB is put into a Mac or Linux box, they can do whatever.

Format NTFS and set All Users to Read-only access

Another easy way to make a USB drive Read Only is formatting the drive as NTFS. This is not recommended because the NTFS file system is what we call a ‘dynamic file system’ and is always changing. Meaning, the User will need to Eject the drive, not just yank it out of the USB socket. If you decide to format as NTFS simply modify permissions so that All Users have just Read Access. The work around is a User modifying the permissions by Taking Ownership and setting Full Access again.

Permanent Read-only

So what about those USB drives that are permanently read only? No matter what you do, on which computer, you cannot remove the read only setting? The answer is this: The read only setting was done at the controller level.

What this means specifically is the USB controller chip on the flash drive ‘controls’ what happens to the data on the flash memory. One feature the controller can perform is to block the SCSI write command to the NAND memory. This is what makes the USB stick read only. The write command is blocked at the controller level. This means the setting is within the USB stick itself and is not dependent on the PC telling the user what it can and cannot do, but rather the device itself is telling the computer what it can and cannot do.

Make a USB Read Only

Unfortunately there is a very large number of USB controller manufacturers which all use their own set of commands to block the SCSI write command. With that said, there is no universal solution to set the read only attribute to all USB flash drives!

Useful Software and Download

On Windows-based systems, you could use the following freeware utilities to set USB devices as Read-Only, od disables them completely:

  • Phrozen Safe USB: a tool you can use to manipulate the status of connected USB devices. You can easily deactivate USB devices connected to your system, make them read-only or re-enable them later.
  • USB Write Protector: enables or disables the write protection for all USB devices of the running system, e.g. USB sticks or external USB hard disks.

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