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I know there are tools on linux that can do this (sfill) as well as windows (ccleaner). However I would prefer FOSS that does this. To my knowledge Eraser does not wipe free space... If it does I stand corrected.

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up vote 3 down vote accepted

Eraser by Heidi Computers can erase unused / free disk space: http://bbs.heidi.ie/viewtopic.php?f=2&t=6307

It is released under GPL.

That said, you might want to consider your exact security needs. You should be aware that wiping free disk space may still leave remainders of files lying about:

  • Programs may leave begin temporary files with confidential data. These are not free space to the OS and filesystem, hence will not be wiped.
  • It may not be possible to wipe all unused areas because of filesystem / OS limitations. Eraser will try to warn of this, but the devs might have overlooked something.
  • You might simply have forgotten that you kept a copy of a sensitive file somewhere.
  • Parts of the data might be in the pagefile / swap file. Consider wiping that as well (but check how to do this correctly, otherwise your OS might refuse to boot!).
  • The storage device may relocate data behind your back: Both harddrives and SSDs will relocate data transparently in case of medium errors or for wear leveling (SSDs). In that case writing new data to a sector with existing data will actually write to a new sector, instead of overwriting the original data. Of course, actually reading this "residual" data may require some hardware trickery.

In my opinion, if you ever worked with sensitive data on a partition (especially if it's an OS partition where temp and OS storage is located), the only safe option is to wipe the whole OS partition plus any data partitions you used. Modern filesystems just do too much behind your back for any other method to be safe in general.

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I don't have access to a machine with it installed at the moment, but I'm pretty sure that Eraser has the option to wipe the unused part of a hard drive and possibly wipe something called tool tip clusters (not 100% sure about that term)?

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