5 Ways to Create Fake Dummy File on USB Flash Drive to Enable Write Protect and Prevent Modification

One of the most common ways to transfer a virus from one computer to another in more recent years has been through infecting files on a USB flash drive because of its portability and the ease at which threats can be passed between machines. A common way to infect a USB device is through the Autorun function present in Windows although Microsoft took steps to eliminate this threat by default, so now a USB flash drive autorun.inf file shouldn’t launch when the drive is inserted.

There are still many other types of threat that can get onto your flash drive though, and plugging it into a computer that is infected with a virus such as JambanMu or MaxTrox can infect a USB flash drive and bind itself to the executables. There are various other methods to protect a USB drive from becoming infected by a virus, one of which is to enable an option in your Windows registry that can turn on a software write protect option to prevent anything being written to the drive while it’s attached to your computer.

You could also buy a device which comes with a write-protect switch built in, and this is a good idea if you plan to buy a new stick that will spend a lot of time connected to other computers, but is obviously not an option for your current devices. There is another way that you can help prevent a virus from infecting your USB flash drive which is by filling up the empty space so that it will be full and there will be no space left for the virus to write itself to the drive. These tools below create dummy fake files to fill the drive up to the very last byte leaving no room at all for anything else to be written and prevents further writing.

1. USB Drive Protector

USB Drive Protector is a dual role program that can create a dummy file (or files) to fill up the flash drive and prevent any additions to it. There’s also a setting to enable the write protect option in the system registry which will prevent writing to any removable drive you insert until you disable the option again. This does obviously only work on any system you turn this option on from.

USB Drive Protector

The dummy file create option is quite useful because as well as being able to automatically fill up the drive to the last byte for you, it can do so using a single file or multiple files. Using several dummy files is handy as it will work better on FAT/FAT32 file systems to get around the 4GB file size limit. Also, if you want to make changes to the contents of the drive, you can delete just one of the dummy files, make the changes, and then fill up the remaining space. It’s a big time saver for larger flash drives because you don’t have to fill the whole drive again.

Place USB Drive Protector onto your flash drive and then run it, this will allow the drive to be filled exactly when you create a single, user defined size or Automatic size dummy files. They can also be placed in their own folder and deleted from the program individually or altogether. It’s a portable executable and works on Windows XP and above.

Download USB Drive Protector


2. Create Dummy Files

Create Dummy Files has a number of options available to put a dummy file, or files onto your USB flash drive with the ability to add any number of dummy files you choose with different file names and sizes. Each file can also have different attributes from the selection of Archive, Hidden, Read Only, system which can help protect it from being deleted by software or the average user.

Create Dummy Files

If you simply want to create a single dummy file to fill up the available space, launch the executable and then click on the File Size disc icon which will show the list of available drives. Click on the USB flash drive and it will populate the File Size box with the available bytes that need to be filled. Enter a file name into the box and click the add icon to place it into the list, if you aren’t running the program from the flash drive then change the output folder with the folder button. Then click Create.

To get around the FAT/FAT32 4GB file limit on larger drives you would have to create some dummy files under that size, and then let the program automatically fill in the last bit for you. You can also choose the fill character, the default is to fill the file with the letter “A”. Create Dummy Files is completely portable.

Download Create Dummy Files

3. USBDummyProtect

For shear ease of use, USBDummyProtect is about as friendly as it gets. It will create a single dummy file that will automatically fill up your USB flash drive to the last byte, preventing anything else writing to the drive. Simply copy the USBDummyProtect executable file to the USB flash drive and whenever you want to fill up the empty space, run USBDummyProtect and a “dummy.file” will be automatically created until the drive shows 0 bytes free.

USBDummyProtect Create

If you need the space back, you can either manually delete the dummy.file yourself or double click on the USBDummyProtect.exe again which will delete the dummy file.

USBDummyProtect Delete

There is no GUI for USBDummyProtect, it’s free and open source while being only 12KB in size. The program does have a limitation though which is the 4GB file size limit on FAT/FAT32 file systems so you can’t use it effectively on a FAT formatted flash drive with over 4GB free space.

Download USBDummyProtect


4. Dummy File Maker

Dummy File Maker

The Dummy File Maker tool is small, very simple to use and is a tiny portable executable of under 20KB. There are not many options available but it does have the useful ability of calculating for you how big the the dummy file will need to be in order to completely fill the remaining space. It does save you the extra step of having to note this down from the Properties dialog and entering it yourself.

Simply place the program onto your USB flash drive, run it and the required file size will automatically populate the box, if you want to create a custom size dummy file, untick the “Using all free space in current drive” box and type in the desired size in bytes. This option is useful if you’re trying to fill up a large FAT/FAT32 drive to create files under 4GB. Enter your chosen file name or leave it at the random entry and click the button. The sub folder tick box will create a folder with the same name as the file.

Download Dummy File Maker


5. Using the Fsutil Built in Windows Utility

An easy way to fill up your flash drive without third party software is to use fsutil, a command line tool included in Windows.

1. Firstly, you have to know how much free space is left on the USB drive. Plug in the drive, go to (My) Computer, right click on the drive letter and select Properties. Take note of the “Free space” that is in bytes. The USB drive below has 518,979,584 bytes free space, so a dummy file needs to be created that has the exact file size.

Removable Drive Free Space

Open up command prompt from Start Menu -> Accessories or entering cmd into the search box and type the following command:

fsutil file createnew F:\MyDummyFile {size from step 1}

fsutil file createnew

You will notice your USB flash drive’s LED blinking meaning the file is being created. After the complete confirmation, the drive now has 0 free space and viruses won’t be able to get in. Obviously you change the byte size and drive letter to match your USB flash drive, the name can be whatever you wish. When you want to copy files onto USB, simply delete the dummy file. When you’re done, create the dummy file again using the fsutil command.

Write Protect USB Removable Drive

You wouldn’t want to use these tools all the time because too much reading and writing will make your USB flash drive wear out faster, or in another words, shorten its lifespan. It is a useful method though to stop anything writing to the flash drive, whether it’s from another user or a virus trying to replicate itself.

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