Question :
I have purchased a 2TB USB-stick for a discount price. I thought that was an incredible deal and when I received it it looked great and my Mac even recognises the USB-stick as properly and sees 2TB of available disk space. I can even reformat the drive and it will still remain listed as 2TB… incredible !
But as the brand name on the product and the packaging do not add up, I got the feeling that at least something is off… so I googled some and found that it is common practice with USB-sticks with extreme memory sizes to turn out to be fraudulent or even counterfeit products… in-factory the firmware has been hacked to make the USB-stick appear as a large volume drive, but when in use, but when in use the data copying either stops when the maximum amount of actual (hardware) memory capacity is reached (4GB or 8GB or sometimes even more) or the data copying keeps on going endlessly but is at the same time erasing previously copied data…
That is really bad news…
Now there is a tiny piece of software for Windows that can check if a drive has been tampered with like that : ValiDrive by GRC (Gibson Research Company) …but that’s Windows-only…

Is there any app for macOS that can do the same ?

Answer :
YES there is !
Even though there is no official version of ValiDrive for macOS and drive checking apps like Disk Utility, TechTool Pro, CleanMyMac X and WD Drive Utilities are not (yet) able detect these hacked drives… there is a macOS-app that can :
Drive Capacity Tester by Sascha Simon Software ( available on the Mac AppStore )

Here’s how to use Drive Capacity Tester to verify USB drives :
– plug the USB-stick into your Mac
– if there is still data on the USB-stick, backup all data from it, then trash everything or reformat
– when there’s no more data on the USB-stick, open Drive Capacity Tester
– then, in the list, select the USB-stick
– in the popup window that appears, just leave Size at “Full” and Steps at “Write and verify data” and click the “Start Test” button (there is no nessecity to pay for the Pro-version… but it is of course very kind of you to support Sascha Simon by buying the Pro-version)
– now, if the countdown underneath the “Writing Files” status bar just counts down to zero, just let it finish… if it finishes regularly, you’re good : the drive is what it is supposed to be
– but… if the countdown underneath the “Writing Files” status bar counts down extremely fast, then loops and restarts the countdown… you can be sure that it is a faulty USB-stick
– in that case you can stop the “Writing Files” process as it will probably get you nowhere… (or you can let it run till it finishes, if ever, hoping you will find how much memory space there actually is on the drive

That’s it !

enjoy 😉