How is the capacity of a harddisk faked?

FAT32 has a master table with free space. You can hexedit that master table to show any amount of free space. I've had a floppy disc sized 3.7 GB for ages now.

The hardware is not modified - the file table is simply modified to fool the OS. During a format the file table gets wiped and thus the genuine capacity reading is restored.

You can get caught by these type of cheap fake flashdrive or even hard drives in China all the time if you go to a non-reputable seller.

Until I saw your message I was sure it was a different controller - using a modified controller, you can tell anything you like to the OS. But given that the format modifies this behaviour, it means that some kind of trickery took place in the file system level as well. This raises two options:

• This is a modification of the controller that simply doesn't work after formatting because it depends on a file system modification (which still seems to me as more likely).

• There is another way to do this without a hardware modification, e.g. by modifying a free blocks linked list to be circular (I am not familiar enough with the specifics of FAT32 to decide if this is possible - might check in a few days if no one else does first...).

EDIT: It is naive to assume FAT32 is being used, a much more likely scenario is that a different file system that inadvertently allows such circular free space management trickery is used (as long as that file system is also supported by the OS - it would be virtually invisible to the user). This makes looking at such a device much more interesting...