Secure Shredder is not shredding at all with too large files!

[chris_l]

I very often use the Secure Shredder 1.9.0.0 that's included with Spybot S&D 1.6.0 installation.
It seems to work fine and pretty fast, as long as the file sizes are up to a few hundred MB's.
As an example, I just shredded 4 files with about 200 MB each, set to 4 passes of shredding,
and this operation took my pc, like 30 seconds or so.

However, I shredded a 3 GB file, set to 1 pass of shredding only,
and this operation took my pc just 1 second, maximum.

And earlier, I had 6 files of 3 GB - 4 GB each, pluss 2 files of 200 MB each, set to 1 pass of shredding,
and this operation took my pc.. maybe 5 - 10 seconds.

So I got the feeling that if the file is too large, then Shredder will not shred it properly.

And since I've seen many programs in the past that have had troubles
with files that were above half the FAT-32 limit;
more than 2.0 GB (2,147,483,648 bytes)
- I was wondering if this could be an issue with Secure Shredder also.

So to confirm this, I got a new 3 GB file, ready for shredding.
But first, I downloaded the free (0.5 MB) tool Disk Investigator from
http://www.diskcleaners.com/files/dskinv.exe
and installed it.
Then I started it and clicked "View" -> "Directories"
Then I browsed to the 3 GB file, selected it, and clicked the "View" button.
This let me see the sector # that first part of this 3 GB file was occupying.
I wrote it down, it was "Selection Sector: 297104768"
Then I closed Disk Investigator.
Then I started Secure Shredder, and set it to 1 pass of shredding,
then shredded the 3 GB file.
This operation took my pc max 1 second to finish.
Then I closed Secure Shredder.
Then I started Disk Investigator again, clicked "View" -> "Disk"
Then I pasted the 297104768 number into the "Sector" field at the bottom left.
And then I saw that the file was 100% intact. Nothing was shredded at all.

So, do you think it will be possible to fix this issue with Secure Shredder,
or is it impossible because it would have to be almost a complete rewrite of the code?

I really hope you can fix it, though!

Thanks in advance,
Chris

[PepiMK]

I'll take a look. In theorie, it should be easy to go around that limitation. It's a bit deeper than our code -we basically just use the environments EoF (end of file) check - but using the Windows API that would not have that environments restrictions (if they are there, will know soon) should be easy.

[chris_l]

Ah, thank you very much for the quick response,
hopefully you will be able to fix it without too much trouble, then! :-)

[PepiMK]

I uploaded a test version here. Worked fine for my 2.1 GB test file, and I did add a few internal tests that compared the contents before deletion to make sure it was fully overwritten as well.

[chris_l]

Yes, I downloaded it and tried it right now on a 4.2 GB file,
it took several minutes to finish, and there were only 0's in the sectors afterward!

Thank you again for your very quick fixing of this tool!