How do I do "wipe" in WinNT

Werner Koch
Tue, 31 Oct 2000 11:00:46 +0100

On Tue, 31 Oct 2000, Wesley J Landaker wrote:

> (this does exactly what most utilities like shred do--overwrite with
> '1's, '0's, and random bytes. Of course, you need a better random
> source than "rand()" usually, but this should probably be okay
> anyway--heck, we're using 50 iterations!!!)
The RNG is not the problem - the problem is that all those program just don't work reliable - see the recent thread on Bugtraq on the shred utility. Shred and also your program assumes that the filesystem alwas oberwrite existing blocks - this is not always true and it depends on many paramters to get it right. The only reliable way to wipe out files is by using a feature of the filesystem - only the filesystem and the kernel do know where the bits are really stored and they must have a facility to overwrite them. The ext2fs has the "s" attribute (man chattr) to do this - however, afiak, this is not implemented. The upshot of this is that you should not assume that a utility like shred or wipe really does what it indends to do. It may do it - but don't count on it. A more realiable way to do this is by creating a small partition for plain text files and then do something along the lines "cat /dev/urandom >/dev/hdxn" - but this is not very practicable. The drive itself my also do wierd things. And for NT you should have a close look at the source (which seems to be available now in St. Petersburg ;) to decide whether your utilty has a chance to to what it should do. Werner -- Archive is at - Unsubscribe by sending mail with a subject of "unsubscribe" to