07 - All about 'Fake' SD cards and USB Flash drives

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FakeFlashtest video


The most common problem you will have with flash memory devices is that they have been 'faked'.
'Gimmicky' USB Flash memory devices and devices that are 'too cheap' will usually be fake (even if bought from a retail store or Amazon!)..

Note: FakeFlashTest was designed to quicklycheck if flash memory devices are fake (i.e. they have been programmed to lie about their size), it does not check all memory for faults..

FakeFlashTest.exe - Diagnosed a fake 16GB USB Flash drive in 27 seconds!

FakeFlashTest.exe - test your suspect 'fake' SD card or USB Flash drive in just a few minutes (rather than hours!) - read my blog.

FakeFlashtest Downloads are at bottom of this page.

If Windows Defender blocks the download, you will need to download the password-locked zip file (password is 'fake').

Please Note: FakeFlashTest
downloads on this page do NOT contain viruses (you can upload the .zip file to www.virustotal.com to check it for viruses).

Note: Some people have found that the FakeFlashTest Quick Size Test fails all the devices that they test.
This seems to be due to something that has been installed in Windows (e.g. Anti-Malware or Anti-Virus software or perhaps a driver).
If you reboot Windows in
Safe Mode (press SHIFT key whilst clicking on Restart) and run FakeFlashTest in Safe Mode, the Quick Size Test should work correctly.

Help! FakeFlashTest destroyed my flash drive\SD card!

You may find that your memory device 'worked' before you used FFT, but now you cannot reformat it.

FFT only reads and writes the normal, standard sectors on your memory device. It does not do anything 'special' to the device.

The most common reason for this is that you are trying to format it as an NTFS volume.

The reason it used to work when you first received it, is usually because it was formatted as FAT32.

The NTFS file system writes it's 'directory' at about the 3GB point on a drive and also performs extensive checks at other points on the drive. If large files are written to an NTFS volume, the data will be written to sectors that are past the 3GB point on the drive (which may not exist!). If your device is fake, you may not be able to format it as NTFS. Also Windows will not let you format it as FAT32 if it is over 32GB in size.

A FAT32 file system keeps it directory, file entries and files at the bottom of memory and fills memory from the bottom upwards.
By using FAT32, the thieves can avoid you detecting that the device is a fake until you have filled up the 'real' memory and by then you will have given them good feedback on eBay!

You can use RMPrepUSB to format it as FAT32 again (but it will still be faulty!).

Photo Fill Test

If you don't want to format your memory device, you can use this test, but be warned that if the device is a fake, then the test (which only copies files) can cause all your other files to be corrupted and lost!

This test can take a while!

It makes folders named \TESTDIR1, \TESTDIR2, etc. and puts 100 copies of the test picture in each folder.

1. Find a large .BMP bitmap file or .JPG file or .PNG file (the larger the better - e.g. 10MB or larger!)
The test script will accept a TEST.MP3, TEST.MP4 or TEST.AVI file as the source file, but you may need to actually play them to check they are not corrupt.
2. Copy the file to your memory device and rename it as TEST - e.g. TEST.BMP or TEST.JPG or TEST.PNG, etc.
3. Copy the file CopyTest.cmd to the root of you memory device (unzip it first)
You should now have these two files on the root of your memory drive:

\TEST.BMP (a large .bmp or .jpg or .png file)

4. Double-click on CopyTest.cmd and press ENTER to start the test
5. The test will stop when the drive has been completely filled with files. You can press CTRL+C at any time to abort, or press CTRL+S to pause the test and then view the files in Explorer.
You can resume the copy process by running CopyTest.cmd again.
6. Now view the last \TESTDIRn folder (e.g. \TESTDIR53) using Windows Explorer - View - Medium Sized Icons.
Check that all the thumbnails in each folder are displayed correctly. Note that there may not be 100 files in the last folder if the drive was full.

You can delete the \TESTDIRn folders when you have finished checking the thumbnails.

'SD Insight' smartphone app for SD cards

You can download the free Android app SD Insight from the Google Play App Marketplace which will reveal the manufacturers pre-programmed details of your SD card. This does not actually test the card, but it can give a good indication of whether the card is genuine or not.

There is also a Google Play free app. called 'SD Card Tester' that will write a large file to your SD card (slowly!) and read it back here (note: double-tap to change folder).

See here for many examples of fake SD cards and how to visually check one.

What is a 'Fake Capacity' USB Flash Drive or SD card?

Many USB flash drives and SD cards are being sold on eBay and other auction sites at very cheap prices (too cheap!). These USB pens are usually of a high capacity (16, 32GB, 64GB or 128GB) and usually from the Far East, but some UK sellers also sell these too. 98% of these sellers are selling 'fake' USB Flash drives (fake UFDs) - either knowingly, unknowingly or I-don't-really-want-to-know-ingly!

There are two types of 'fake' 16GB USB Flash drives...

Most Flash drive and SD cards are pre-formatted as FAT32. The directory and file names on a FAT32 device are all located in the first few MBs at the bottom of memory.
The actual file contents (data) are stored above the directory.

It is similar to how a book library uses library cards. The library cards are stored at the bottom of memory and the actual books are stored higher up in memory.
If you destroy the library cards, then you (Windows, linux, your camera/smartphone) cannot find any of the books.

2MB+ Actual file data
1MB File directory and names and a pointer to where the file contents is located
0 MB Partition table

Type A
With a Type A device, you can copy 16GB of files to it and it will appear to have stored them all. If you look at the memory device using Windows Explorer, all the file names will be there and it will look fine. You will be able to access any files that are stored on the device up to the 2GB point. Any files stored after 2GB will be corrupt (probably all 0's or 1's).

Type B
These memory devices will appear to work until you put too many files on them (e.g. in the case above, if you put more than 2GB of files on it.) Once you exceed the true memory capacity, the next file that you write to it will actually start writing at 0MB which is where the file directory is located. This means that the file directory is now corrupt and you cannot access any files at all!

Be careful!

If you buy one of these fake UFDs or SD cards, they will appear to work fine and Windows will show them at their 'rated' capacity - for instance a 64GB UFD will appear in Windows to have a capacity of say 61.3GB, you may even give the seller positive feedback on eBay because they appear to work fine. However, these UFDs actually only contain about 2GB of real memory. When you start putting your files onto it, everything may appear to be fine - until you fill it up with more than 2GB and then it completely corrupts all the files on it! Bet you wish you hadn't paid £20 for it now!

The fake product is usually made from a poor quality or defective smaller flash memory chip (and probably a 2nd rate 'reject' memory chip obtained from the trash can at the back of the factory!), but the controller has been programmed to falsely report it's capacity as say 64GB to Windows.

Don't be caught by these cheats. Simply ask them to test the UFD using RMPrepUSB - Quick Size Test, FakeFlashTest or H2TESTW before you buy it. If they refuse then walk away from the deal! Explain to them that if the UFD passes H2TESTW they will get a lot more bids if they state this in their adverts.

Do you have a fake Kingston Flash Drive? One simple way to check, is that usually Kingston print text onto the metal USB connector which has the model number and capacity + other numbers. If your Kingston drive has no printing on the connector, it may well be a fake!

Buying from eBay, Amazon, etc.

WARNING to all eBay and Amazon buyers - Always check the seller's feedback - if anyone has given ANY neutral or negative feedback because of 'corrupted' data, then it is likely that the product is counterfeit/fake. These devices will appear to work to start with, and do not fail until after you have left positive feedback!

Always test the memory using RMPrepUSB - Quick Size Test or FakeFlashTest before you use it. It would be a shame if you used a 64GB SD card for all your photos on that 'once-in-a-lifetime' holiday to Africa, only to find out that all your photos have gone! Also, please ensure you give the seller negative feedback and report them to eBay for selling fake goods - if they knowingly continue to sell fake goods they are criminals and don't deserve good feedback! Also, get the eBay seller onto the eBay Fake Sellers list here.

Buying an SD card on eBay? - If you are buying an SD/SDHC card from an eBay seller, check the full description very carefully. Some sellers are advertising a '16GB SD Class 10 SDHC card' and then in the description say 'these cards have been tested and may vary from 2GB to 32GB' and 'this is normal for cheap cards' and even 'the data you store will be compressed so don't worry if you can only store 2GB as really you can store more'. This is all a load of rubbish! These cards are 'fake capacity' cards and have been deliberately manufactured to deceive the buyer! eBay seem quite content to allow these sellers to sell their fake goods and even allow them to pretty-much state that they are fake!

How to test a suspect UFD or SD card


If you have a USB Flash drive, try using ChipGenius as a first test and very quick 'test'. Often this will reveal the true size of the memory chips(s) fitted by the manufacturer. The screenshot below shows a fake 16GB USB Flash drive containing a JS29F16G08AAMC1 memory chip which is a 16Gb (Gigabit) or 2GB (GigaByte) memory chip. It therefore cannot possibly hold 16GB of data!

Tip: For testing SD cards, buy a USB 3.0 card reader for £5 from Amazon - these really improve data transfer times (even if just using them on a USB 2.0 port). Cheap USB 2.0 card readers are notoriously slow!


FakeFlashTest was designed to test for these 'fake' memory devices. It does not test every bit of every byte, it just looks for missing chunks of memory and so is much faster than other tests.
FakeFlashTest.exe - Diagnosed a fake 16GB USB Flash drive in 27 seconds!


If you have bought a 'bargain' UFD, you can test it using the 'Gold Standard' test H2TESTW written by Harald Bogeholz for c't magazine. This test is very thorough but very slow because it tests all bytes of unused memory (even if it doesn't exist).

The test utility is not included in the RMPrepUSB download but there is a link to the download on the RMPrepUSB help form - Just run H2TESTW.exe and select English as the language and the empty USB drive that you want to test. H2TESTW will fill up the empty, unused space on the UFD with large files but will not destroy any files that you already have on the UFD (but it you may lose all the files if the UFD is a fake one due to corruption!). The test can take 4-8 hours to test a good 16GB drive and considerably longer if it is faulty.

BE WARNED: If you already have photos/files on the memory device - copy them first (take a backup). Filling up the memory device with more files can cause the existing 'good' files to be corrupted and lost!