Unfortunately, you can never be sure. As someone pointed out, some filesystems take snapshots. So things like 'shred' and rewriting the entire filesystem with zeros over and over again are the best you can hope for.
The NSA and DoD require that the drive be physically destroyed. They degauss it and often then hit it with something large and heavy. It then has to be certified that it's beyond recovery. http://www.spectrumwest.com/Attach2.htm As you might expect, this is actually a lot of trouble for an IT-heavy place like the NSA or most DoD facilities these days -- lots of media to take care of -- so the more practical solution is to toss it in a cardboard box and leave it in a vault for eternity, or at least until some (infrequent) mandate from up on high comes around for them to clean up such things. -- Brian C. Merrell [EMAIL PROTECTED] On Tue, 1 Nov 2005, 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? >
