Kevin Kalupson wrote:
I have a curiosity that I would like to indulge.
I'm wondering about deleting a file in a secure manner. Something
similar to an NSA or DOD wipe of an entire hard drive. Does anyone
know of a utility script to do something like the following or would
it be more complicated?:
1) Obtain the file size that is to be deleted
2) Obtain a string of data from /dev/urandom exactly the size of the
file that is to be deleted
3) Open the file for writing
4) Over write the file
5) repeat steps 2-4 n number of times
My major uncertainty is whether or not there is a automatic guarantee
that the file will be over written in the exact same spot on the
physical HD.
If this is possible, are there differences in file systems that would
affect the solution, such as one appropriate method for an Ext3 that
would not work for Reiser?
There is no guarantee that a filesystem will write over the same
blocks. If you wanted to go this route, I would use debugfs to find and
modify the blocks in question. Here is a site about recovery which
describes how to find which blocks a file is using:
http://www.tldp.org/HOWTO/Ext2fs-Undeletion-10.html
