Re: How to "wipe" ALL Mac file's slack space?

In article <santa-30D03E.19472829062007@xxxxxxxxxxxxxxxxx>,
Santa Claus <santa@xxxxxxxxxxxxx> wrote:

i once wrote a program that wrote a block of zeros
in the slack space by the following method.

- - - and - - -

i wrote it mainly to make compressing files
and folders much more effective and it worked.

Bless you, thanks for sticking to the main topic of this thread when
most others go off topic with personal attack barbs.

Messing with cluster slack space is exactly what I am trying to do, in
order to make compression of files much more effective.

Lemme go off topic a bit in order to further clarify that
hard-to-understand term "cluster".

First off, I was dead wrong on one point, not clear enough on another
point, when I stated earlier:


Correction and clarification begins
***********************************
"A cluster is a fixed size, determined by the file system; with the NTFS
system used by Intel Macs, the default cluster size is 4KB."

With further checking, I learned that cluster size is NOT determined by
the file system, but rather by the OS.

I was also very unclear when I stated:

"with the NTFS system used by Intel Macs,"

What I intended to say was:

"with the NTFS system used by Intel Macs in
their BootCamp created Vista partition..."
*********************************************
End of correction and clarification


Sorry about that, there is nothing worse than being wrong about a
hard-to-understand term like "cluster", it just further confuses an
already confusing term.

A file 'cluster' just basically means a bunch of file fragments, of only
ONE file, scattered all over the physical hard drive in different
places. Such a scattered file is said to be "fragmented".

Each individual file fragment is made up of a bunch of contiguous
"sectors".

Read that slowly, the sectors in any given bunch ARE contiguous, but the
individual file fragments themselves are NOT contiguous, those fragments
of one file are scattered all over the physical hard drive.

A "cluster" is totally different than a "block".

A block, as used in computing, _could_ contain many different files.

A cluster, as used in computing, can contain only one file.

Cluster, as used in computing, is really short for:

"a cluster of more than one piece of an individual file"




i once wrote a program that wrote a block of zeros in
the slack space by the following method.

1) get the current eof position.
2) set the current write position to the current eof.
3) write a cluster of nulls (hex 00) to the end of the file.
4) reset the eof of the file to the original position.

this must be done with every file.

I hope to bypass all that work by locating a utility that someone else
has already written, being inherently lazy myself.

Windows users have such a utility, it is called "KillDisk" version 5.0
(earlier versions will not wipe slack space)

With lots of luck, I might be able to locate a similar utility that will
work with Mac hardware.

Mark-
.

Relevant Pages

  • Re: Looking for Free Slack Space Wiping Util
    ... > allocated cluster is used and the unused part of the last cluster ... > it also opens a potential security problem when overwriting unused ... it doesn't appear to erase slack space ... >> AFAICT - does handle free space; ...
    (alt.computer.security)
  • Re: Finding REALLY hidden files?
    ... The disk storage for a file is allocated in fixed size units called ... This means that if the cluster is 32KB and the file length is 12 times ... but slack space is slightly different than the space ... Virtually all hard disk drives use, at the physical level, a sector ...
    (rec.video.desktop)
  • Re: Harddrive used memory
    ... Manufacturers quote disk sizes in decimal GB, ... determined by the file system you're using (FAT32 tends to use bigger ... Any file, no matter how small, will occupy at least one cluster. ... 37GB are probably being lost to slack space. ...
    (microsoft.public.windowsxp.general)
  • Re: Finding REALLY hidden files?
    ... Any left-over space in the last cluster of a file is lost, in that it will never be used for any other data. ... but slack space is slightly different than the space ... Virtually all hard disk drives use, at the physical level, a sector ... if the cluster size is 32 KB (and under FAT32 I *have* had drives with clusters that big) and you create a file of length one byte, it is not just the 511 bytes in the first sector that are lost to further use, it is also the 512 bytes in each of the other ...
    (rec.video.desktop)