Why 'rm -R star' Isn't Enough

zdburke writes: "Short but interesting article in the New York Times (free reg req'd) about how difficult it is to cover your digital tracks because electronic documents are so well distributed -- on your lap top, on your workstation, on the server... Yes there are tools to thoroughly delete files on your computer, rather than just unlinking them when they're put in the trash, but it's the distributed nature of content these days that poses a special problem to the Ollie North's of the world."

Comments

Mirrors

[alsta]

If you're afraid that mirrors will copy your files, why don't you just overwrite the file with the same name, just some bogus data. That file will be mirrored again since it has a new date.

Sometimes when a problem gets high tech, it's time for a low-tech approach.

Why no discussion of file slack space?

[Goldenhawk]

I'm surprised I've seen no discussion here of the very basic problem of file slack space - that unallocated space at the end of the last sector of every data file, except those that exactly fill a disk sector. Most of the methods described here for easy ways to wipe empty hard drive space do not overwrite all the file slack space. You need a program that does that explicitly. Otherwise every sector with the tail end of a file contains easily recoverable data, although disassociated from any filename. Given that the slack space on a hard drive averages out to $sectorsize*$numfiles/2 (on average, 1/2 of a sector, times the number of files), the average 40Gb hard drive with 10,000 files might have 50Mb or more of recoverable data, even if the "empty" space were completely and unrecoverably wiped.

I learned about this while preparing to publish a program commercially, and discovered that (at least at the time) files I copied to the distribution media master sometimes contained sensitive data, such as the source code, from my own hard drive. Basically, DOS wasn't very picky about copying a few extra bytes along with the actual file length, as long as the extra bytes didn't go past the end of the destination sector. The answer? I used a slack wiping program on the master disk before sending it for duplication.