CC Drive Wiper less effective for external drives?

CCleaner for Windows
1

Hello,

I've been using the Drive Wipe Free Space function in CCleaner on both internal hard drives (eg: c:) and external USB drives (a hard disk and some memory sticks).

After using wipe free space on the internal drive I ran Recuva to see if it found anything, and it reported zero files.

On my external hard disk and memory sticks, Recuva finds all the files that were previously there, though reports them as having been overwritten and unrecoverable. It seems to me that with external drives the data has been successfully overwritten, but that there's a filename table remaining. I'm not worried about the data being recoverable, but the deleted file names are clearly available to anyone who cared to look.

Is there some reason for the difference, and how do I wipe free space on USB drives such that old/deleted contents can't be listed?

For info: CC v4.14.4707, Recuva v1.51.1063

Piers.

2

If the drives are formatted as FAT32 then I don't think that the directory is wiped, so the old file names will still be seen, unlike NTFS where the Drive Wiper includes a wipe MFT in a wipe free space.