Can a fake drive fake a full format?

[rd369151]

Can a bad/fake drive fake a successful full/long format?
That is, either in Windows, or programs like "SD Card Formatter", when told to literally format and check every sector, can a fake drive fool the formatting program into thinking it really has formatted all the sectors the drive is supposed to have?

 

[miquelfire]

My understanding on how formatting works is that the formatter would just write zeros during a full format. If it has a check for bad sector feature, maybe it will write some dummy data to the sector and check to make it write correctly before just storing a zero value.

If the fake drive is doing some First In First Out style of fake space, or a remap of sectors so even though it has less than a quarter of the advertised space data will still be stored, this will pass that test. If it's the common "I have 1TB" but it only has 200GB, then anything after that 200GB will fail.

 

[PHolder]

I think a full Windows format just blanks the LBAs and if the drive subsystem doesn't complain that a write fails, Windows doesn't actually subsequently verify that the contents got into the state it desired. A drive that lies about successful writes should totally fool it.

TL;DR: Yes, I assume that is easy for them to do.

 

[rd369151]

I'm going to have to look back at the non-Windows format tools, and see which claimed to do some validating of the drive, but maybe they really don't. after all.

 

[SeanBZA]

Even if they validate, they are checking a current block, so the drive will still pass, as it simply is overwriting the older ones (aside from those that are faking a FAT filesystem on the drive) time and again. you would have to write each sector with pseudorandom data, store a hash of each block in RAM, and after finishing writing the entire drive, then read each block back, and hash it again, and compare to the hash stored in RAM. And discrepancy is marked, and you then will see just how big the underlying real storage is after it is complete.

 

[rd369151]

This being a technical crowd, I though y'all would be familiar with "Rufus: The Reliable USB Formatting Utility" that has as one of its Features

* Perform bad blocks checks, including detection of "fake" flash drives

"Perform bad blocks checks, including detection of 'fake' flash drives".

Elsewhere he states that:

By default, Rufus will check for fake USB flash drives that pretend there is more capacity than actually is by looping over the flash. This check which is enabled by default is performed by writing the block number sequence and reading it back during the bad block check.

But also:

So, please let me make that absolutely clear again: While Rufus can do bad blocks checking, it is only provided as a courtesy and Rufus was never designed to be a fully fledged bad blocks check application.

 

[rd369151]

A related question, that I've suggested in another thread, is that if even a native Windows quick format let's a suspected fake drive attain its specified capacity, then is it something that ValiDrive is concerned with?
I.e., at that point what we have is just a counterfeit drive, e.g., "brand X" vs. SanDisk, and something that really wouldn't be safe to use, and only useful to keep as an example to compare to future purchases.

An even more tangential question is how much proof would we need to send the drive back to Amazon, if caught in time?

 

[jlee]

Can a bad/fake drive fake a successful full/long format?
That is, either in Windows, or programs like "SD Card Formatter", when told to literally format and check every sector, can a fake drive fool the formatting program into thinking it really has formatted all the sectors the drive is supposed to have?

Given that SD Card Formatter deals with flash memory, writing every sector with a sector number or some kind of unique signature leaves all the flash as written. This means to use the flash afterwards the flash device has to erase it first. Thus it's highly unlikely any flash memory formatter tool would do this kind of test by default. All these tools typically do even when doing a "full" format is to simply read each sector to make sure it doesn't have an error, plus write a few sectors with metadata to create the filesystem.

Also, any flash which is in the erased state doesn't actually get read. The drive simply makes up the data (usually 0s) and sends it to the host. Thus any formatting utility that only does reads can't test such flash.

Thus it's not hard for a fake drive to fool a tool like SD Card Formatter even when doing a full format.

 

[miquelfire]

You actually bring up a good point. If the format utility just reads the sector during checking, but never writes, flash drives might just be trimmed, then relies on the controller to tell you it has valid data, which fake drives may not brother to check (as is their purpose). If the check method is writing to the drive to make sure it's valid however, hopefully if it does the trim command to mark sectors as erased, it does it at the end of the check.

 

[rd369151]

Remembering the days when we had to first do a low level format before the DOS format to those spinning platter drives, I came across something that purports to do the same for these USB drives, that can also restore the full capacity from some sorts of boo-boos.

USB Low-Level Format mentions some points like:

For instance, a USB flash pen drive may contain less capacity than its original state for unknown reasons;

The process of low-level formatting is slow, as the software thoroughly and irreversibly erases all data from USB storage devices followed by restore USB drives to original state to find back the lost capacity and make them back to normal.

And they also provide a USB Drive Factory Reset Tool - Restore USB flash drive back to full capacity since:

You might find it necessary to restore a USB drive after working with tools, such as Rufus, USB Disk Storage Format Tool on Windows to burn an ISO or dd command on Linux, to write an image file to the USB storage drive.

So there are possibilities that a messed up USB drive does not have its full capacity, due to some boo-boo, not necessarily an intentional counterfeit/fake.

But, a legitimate product freshly unwrapped from Amazon should be in a perfectly usable state from the get-go.

(I'm mentioning these tools for those who might have problems due to their own messing up their drives on their own. The Internet is filled with reports like that.)

 

[PHolder]

Steve already produced a tool that is known to solve this issue. https://www.grc.com/initdisk.htm I would definitely try it first before trying anything else, as there are definitely sketchy options out there.

 

[rd369151]

I was referring to those Bureausoft Corporation programs more for sake of their desciptions of what can go wrong.
Personally, I prefer the exFAT format, which GRC's InitDisk can't do.
And also, I really prefer the hand-holding of a GUI for tasks like that.
From the authority standpoint, I would start with SD Card Association's "SD Card Formatter" as they might have a better idea of what they are doing than Microsoft, for those USB drives. Citing their web site:

It is strongly recommended to use the SD Memory Card Formatter to format SD/SDHC/SDXC/SDUC Cards rather than using formatting tools provided with individual operating systems. In general, formatting tools provided with operating systems can format various storage media including SD/SDHC/SDXC/SDUC Cards, but it may not be optimized for SD/SDHC/SDXC/SDUC Cards and it may result in lower performance.

And it does exFAT, not even offering other formats.

As I noted in a different thread, I found that even the simplest and quickest Windows native GUI can restore a USB drive's full capacity.
I didn't even have to try a fancier tool. Now I'm more aware of all the possibilities.