[ Thanks to Falko
Timme for this link. ]
“Sometimes you need to destroy or wipe data from hard drives
(for example, before you sell your old hard drives on eBay) so that
nobody else can access them. Simply deleting data (e.g. with rm) is
not enough because that just removes the file system pointer, but
not the data, so it can easily be undeleted with recovery software.
Even zero’ing out your hard drive might not be enough. Here’s where
shred comes into play – shred can overwrite the files and
partitions repeatedly, in order to make it harder for even very
expensive hardware probing to recover the data.”