Singapore Microcomputer Society

Established since 1978

Registrar of Societies Ref. no: 0238/1978

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Write-Protect USB thumb drive or USB Devices

When you plug in your USB thumb drive into a USB port, are you aware that if that PC is infected with viruses or worms, your thumb drive may get infected too?


The only way to avoid being infected is to write-protect your thumb drive before it is plugged into the USB port ? not after.

Currently, there are basically 3 methods to do so:

  1. Buy a USB drive with a write-protect switch. With that you can write-protect your thumb drive before you plug into someone else's PC.

Sorry.  All our write-protect thumdrives have been sold out.

Buy a USB drive with built-in software write-protect so that you can run the software to write-protect your USB drive. The downside is that you have to write-protect your USB drive before you plug it out of your PC. Otherwise, your USB drive will not be write-protected and when you plug into someone else's PC, you may get infected. It is too late after you have plugged in and then attempt to write-protect it when the virus could have already infected your thumb drive the moment you plug it in.

Many USB drives don't have any write-protection feature. So you have to use a third method which is to configure your PC to disable write access to USB drives. Using this method is simply to write a (value of 1 to write-protect or a value of 0 to unwrite-protect) to the following DWORDWriteProtect value in registry key

HKEY_LOCAL MACHINE\System\CurrentControlSet\Control\StorageDevicePolicies


There are 3 methods to do so. You can run regedit to manually change it. You can also run a program that to do it to simply the number of clicks. You can also run a .reg file that will set the values for you.


Often, it is not convenient to install on someone else's PC just to write-protect the USB drive. Hence, if you have Internet access then you can but we don't recommend you do that unless you really know what you are doing and need this feature badly.

Click here to Write-Protect the PC's USB drives.

Click here to Unwrite-Protect the PC's USB drives.

Your browser will prompt you with warnings as usual. Just open/run it when prompted. After clicking on write-protect, then insert your USB drive.


Remember to Unwrite-Protect the USB drive otherwise that PC will not be able to write to USB devices and the user may think that his PC is faulty!


Note that write-protecting your own PC's USB drives merely means that you cannot write to the USB drives. If you had plugged in an infected USB drive into your PC, your PC will still get infected. Write-protecting USB drives does not write-protect your PC hard disks. That's another story.