Secure Deletion of Data from Magnetic and Solid-State Memory

Secure Deletion of Data from Magnetic and Solid-State Memory

`shred': Remove files more securely

`shred' overwrites devices or files, to help prevent even very
expensive hardware from recovering the data.

Ordinarily when you remove a file (*note rm invocation::), the data
is not actually destroyed. Only the index listing where the file is
stored is destroyed, and the storage is made available for reuse.
There are undelete utilities that will attempt to reconstruct the index
and can bring the file back if the parts were not reused.
On a busy system with a nearly-full drive, space can get reused in a
few seconds. But there is no way to know for sure. If you have
sensitive data, you may want to be sure that recovery is not possible
by actually overwriting the file with non-sensitive data.

The best way to remove something irretrievably is to destroy the
media it's on with acid, melt it down, or the like. For cheap
removable media like floppy disks, this is the preferred method.
However, hard drives are expensive and hard to melt, so the `shred'
utility tries to achieve a similar effect non-destructively.

`Secure Deletion of Data from Magnetic and Solid-State Memory', from the
proceedings of the Sixth USENIX Security Symposium (San Jose,
California, 22-25 July, 1996).
visit: http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html

So. `shred' a linux command : Remove files more securely

shred [OPTION]... FILE[...]

look man page how to use..