From shred man page:
What the above means, is that shred works fine with ext3 in its default mode. And, since shred overwrites 25 times, with a mixture of 0s and random data, and most security experts nowadays agree that 3 iterations will make data unrecoverable by most methods thar don't involve an electron microscope, I'd say shred is pretty damn good.In the case of ext3 file systems, the above disclaimer applies (and
shred is thus of limited effectiveness) only in data=journal mode,
which journals file data in addition to just metadata. In both the
data=ordered (default) and data=writeback modes, shred works as usual.
As for scrub: that isn't in any of the usual repos. I've never even heard of it before.