Question How do I check if my USB flash drive is legitimate, not fake?


Mar 15, 2022
I bought a SanDisk 256GB USB flash drive from a credible source. However, I have some suspicion that it may be a fake. How do I check if the USB flash drive is legitimate or fake?

Is there a program that can analyze the USB flash drive, and tell me if it's legitimate or fake?
I believe there are better ways, but what pop into my mind is this method:

If you're using W10/W11 then you can use the software 7-zip (file compression tool). Go get some large files (you're supposed to fill the usb stick almost full), ISO mages or installfiles for games or whatever - just make sure the file size in total is slightly less than the capacity of your usb stick.

Then use 7-zip to pack those files into one (or several equal sized) file. The settings of 7-zip file dialog box for compressing:
  • Make sure that the 7z file you're about to create are stored on the usb stick (you can of course move it with file explorer later on if you forget this and the 7z file is to be created on an internal storage instead).
  • Make sure the file type is 7z
  • There are an option on how much compression you need (from none to Ultra with several steps between) - the ISO and maybe EXE files are probably already compressed so you don't need additional compression - can be set to None (takes less time and after all that is not the purpose this time).
  • While the 7z file is creating, have a coup of coffee so it's easier to stay awake.
  • After finnished, you open the newly created 7z file (if divided into several smaller files, just open the one that ends with .001 )
    • Then you have 7-Zip to perform a CRC-check on the newly created file.
    • If that CRC test pass, then you can assume the usb stick storage are intact.
There are other tools out there that can perform CRC check on a single file independent on the file type. If you find such a tool and also have a file big enough, you can do a CRC test on the file while on internal storage, then copy it to usb stick and after a while perform the same CRC check on the copy of the big file now located on the usb stick.

And I almost forgot to mention - You may want to remove the USB stick and then insert it again to reduce any risk of getting good crc just because file data still resides in memory buffer.

A third note : Problem with corrupted files can also be a result of bad memory, so you may want to run a test with Memtest just to rule that out.