wipe /dev/sda

[Kent Borg]

Kent Borg a wrote:
> If you are paranoid enough to spend time on this consider the security
> of your data before you are done with your disks.  Do you do regular
> backups?  Are the backups encrypted?  Is your working data encrypted? 
> Do you regularly wipe your old files by filling the "unused" portions of
> your working disk with random data?
>   

And, if encrypting, are thinking it all through? Using high quality
passphrases (that are not recycled on different systems), using high
grade encryption, regularly updating your system, worrying about *where*
you type your passphrase (is there hardware or software recording your
keystrokes?).

Note that /dev/zero is much faster than /dev/urandom. Also note that
computers sometimes get "clever" in ways you might not anticipate. For
example, if you want me to store 10TB of zeros in a tiny space, I can do
it for you. All I have to do is compress it, and if the data is all
zeros, the compression is trivial, I need only note how many zeros and I
never have to haul any bits from here to there. Quality random data, in
contrast, is impossible to compress. If you really want to be certain
the disk stored your data and didn't cheat, store random data.

Finally, if you only store encrypted data on your disk then there is
little need to wipe the disk before disposing of it.


-kb