Messages in this thread | | | Date | Thu, 23 Jul 1998 13:36:47 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: Secure deletion |
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On Thu, 23 Jul 1998, Alexander Kjeldaas wrote:
> On Thu, Jul 23, 1998 at 09:14:44AM -0400, Richard B. Johnson wrote: > > > > If you don't need 'instantaneous' security, i.e., you can clean up > > your disk(s) once a day, just make a program that writes a file, > > filled with "SECURITY ", until the disk partition is full. > > Close the file, sync the file-system, then delete the file. > > > > This probably won't work for a block that has been reused in another > file, but where the whole block hasn't been overwritten by the new > file. Let's say I have a 100k file, delete it and create 100 1-byte > files which occupies the blocks from the 100k file (blocksize 1k). > Then there will be 1023 bytes in each block which are allocated, but > with unknown state. Whether they are overwritten by 0s or not written > at all is unspecified. >
There are always things that "won't work". If your disks are "cleaned" each night, you will find a high probability that the unwritten data will contain the security pattern. In fact, since I started using this technique (two years), I have never seen any unwritten data that didn't contain (1) The rest of the sector-buffer, (2) The words "SECURITY" with 8 trailing blanks.
Cheers, Dick Johnson ***** FILE SYSTEM MODIFIED ***** Penguin : Linux version 2.1.108 on an i586 machine (66.15 BogoMips). Warning : It's hard to remain at the trailing edge of technology.
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