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1.
Introduction 
Shredder literally destroys files,
free space and your Recycle Bin contents instead of only deleting
them. That means your data contents one overwritten and destroyed
and can't be recovered.
The user therefore should be sure of the files, folders …etc.
he/she wants to shred.
There are many safeguards built into the shredder program to warn
the user.
Shredding
disk's free space
Windows allocates clusters for
new files (and extending existing files) from one end of the disk
and moving towards the other end. Accordingly, the user for example
if deleting files near the end of the disk, it might be very long
before those clusters get used again. Therefore, the unallocated areas
of the user's disk may contain bits and pieces of those files that
were deleted weeks or months ago, and thus information could be vulnerable
to anybody who knows where and how to look for it.
Therefore, shredding a disk's free space ensures that any deleted
data stored in unallocated clusters will be completely shredded, and
all the bits and pieces of left over data from deleted files will
be destroyed.
Generally
speaking Windows stores
files using two steps:
- A directory entry &
- A series of one or more clusters on a disk.
The directory entry contains all
the information about that file (name, size, data stamp
info, and starting cluster number). The data of the file is contained
inside the clusters.
When the user deletes a file using windows the file's data doesn't
actually get deleted from disk. Windows simply marks the file's clusters
as available for reuse, then marks that file's directory entry as
deleted (from the directories available) by replacing the first character
of the file's name with a special character. Now if those clusters
don't get reused for another file, they are vulnerable
and can be retrieved by those who know where and how to look for it.
Adding one byte to the directory that was deleted will allow the retrieve
of the entire file that has been deleted. This is used in most of
the "Unerase" utilities functions.
Shredder makes it virtually impossible to retrieve data from a file
because it literally overwrites the file's data clusters before deleting
the file. A "quick" shred overwrites the file once,
filling its data clusters with zeroes. This is sufficient to prevent
casual efforts retrieve the data. A "Thorough" shred
overwrites the file maximum 10
times, using varying bit patterns each time, so that the disk's
magnetic contents are scrambled beyond any possibility of recovery,
even by those who might use dedicated hardware to examine the disk.
Shredder also scrambles the contents of the file's directory entry
so that "Unerase" utilities can't tell either what
the file's original name was, or where on disk its data was stored.
The net result is that after you shred a file, its data and all references
to that data are gone for ever.
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2.
Using Shredder
You can run Shredder from the command prompt.
Example:
1. If you want to shred drive E, write "shredder.exe e:\"
2. If you want to shred the Recycle Bin, write "shredder.exe
recycle"
- You can shred files & folders in three different ways:
2.1.
Drag and drop
Drag and drop (Files/Folders)
to the shred files/folders list box.
This is the most efficient way to use shredder, especially when you
have more than a few items to be shredded. The user will receive one
warning prompt, then the shredding will proceed to execute the list
the user dropped.
During the shredding process, it displays the name of the file being
processed and the progress information to let the user estimate how
long it will take.
The cancel button will abort the operation so that shredder will not
process any remaining items on the list. However, the file that was
being shredded when the cancel button was clicked would have been
already at least partially overwritten, so that file is gone and can't
be recovered.
2.2.
Using the browse button
To add files or folders to the
list box.
2.3.
Right clicking association method
By right clicking Files/Folders, drivers or
the Recycle Bin and selecting the "Data Shredder"
item in the context menu Shredder will present a single confirmation
prompt, and then proceed to shred the items in your selection.
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3.
Main Shredder Window
The main shredder window has the following tabs:
| 1. Scheduler. |
2. Shred Files. |
3. Shred Folders. |
| 4. Shred Recycle Bin. |
5. Shred Empty Drive Space. |
6. Shred Options. |
3.1. Scheduler
This option allows the
user to choose a task in the scheduler task list box and then
set the different options (see screen shoots) for a specific
interval, a starting and ending at specific date and time. There
is also a power management option that avoids shredding in laptops
when power is low etc.
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3.2.
Shred Files
Gives
the user the capability to browse, remove item from the list
box after selecting it by dragging and dropping or removing
all the items selected,and a button that takes the user to
the schedule window to set up the way and properties of the
schedule.
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3.3.
Shred Folders
This
window has the same options as Shred Files except it
has an option to select subfolders.
This dialog lets you determine how (or if) Shredder will process
the subfolders of any folders that you shred. By default, both
of these options are set to Never so that Shredder will
not process subfolders at all.
(i) In the Shred contents of the subfolders section:
Never means that Shredder will skip
over any subfolders.
Prompt means that Shredder will ask you before
shredding each subfolder
(And subfolder thereof).
Always means that Shredder will process all subfolders
(And subfolder
thereof) without asking you first. However, Shredder will
always prompt you
before it shreds a folder that has the "System" attribute set. This usually (but
not always!) indicate that the folder is required by Windows
itself. It's up to
the user to decide whether or not that is the case, and
thus whether or not it is
safe to shred the contents of that folder.
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(ii) In the Remove subfolder after shredding section:
Never means that Shredder will never delete the
subfolder itself after its contents have been shredded.
Prompt tells Shredder to ask you before removing
a subfolder.
Always means that Shredder will remove a subfolder
(if possible) without asking you first.
Note that a subfolder can't be removed unless it is completely
empty.
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3.4.
Shred Recycle Bin
Presents
a warning prompt, then shreds any and all files and folders
currently stored in the Recycle Bin.
Note that the Subfolder options settings don't apply to this
function.
Shredder will shred every thing the Recycle Bin contains, regardless
of any individual file/folder, or subfolder attributes.
This command requires a
specific internal Windows function to do its job properly. This
function resides in the SHELL32.DLL component.
Shredder processes the Recycle Bin one drive at a time. For
each drive:
- It queries the status of the Recycle Bin on that
drive. If the Bin is empty, Shredder moves on to the
next drive. If the Bin is empty on all drives, Shredder
presents an appropriate message and returns to the
main window.
- It shreds the files currently stored in the Recycle
Bin on that drive. The progress dialog shows the name
of each file as it is stored in the Bin. This may
or may not be the same as the file or folder's original
name, depending on how the file or folder got moved
to the bin. When you move individual files to the
Bin (whether singly or as a group), Windows renames
them using its own internal scheme. The file's extension
is retained, but its base name is replaced with a
"serial name" consisting of the letter "D"
(for "Deleted") followed by the drive letter
and a sequence number. If you move a folder to the
bin, that folder gets renamed using the same scheme,
but any files and folders it contains do not.
- To avoid problems with Windows' internal mechanisms,
Shredder can't rename or delete files or folders that
are stored in the root level of the Recycle Bin. Therefore,
it waits until it has shredded all of the Bin's files
and folders on the current drive, then tells the system
to empty the Bin for that drive. This allows Windows
to delete the files and folders and maintain its index
properly.
- Canceling this operation will leave all root-level
files and folders in the Bin on the drive being processed,
whether or not they have been actually shredded. You
can tell whether or not a file was shredded by checking
its size-shredded files will have been truncated to
zero bytes in length. Any file that is not zero bytes
in length has not been touched and can be safely restored.
To determine whether or not a folder's contents were
shredded, you must restore that folder. Any files
that the restored folder contains have not been touched.
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3.5.
Shred Empty Drive Space
Presents
a warning prompt, lets you choose which drive to shred, then
shreds the free space on that drive according to the current
settings.
Choose a drive to shred:
Use this dialog to tell Shredder which drive you want processed.
You can either type the letter of the drive you want, or click
the arrow to open the list and see which drives are available
(you may only shred free space on local non-removable hard disk
drives), then choose one with either the mouse or the arrow
keys.
Click OK (or press Enter) to accept your selection
and continue.
Click Cancel (or press Esc) to abandon the operation
and return to the main window.
Note that shredding large
amounts (i.e. gigabytes) of free space may take several hours,
especially if you're using the Thorough shred option.
Since Shredder allocates
and locks all available free space on the selected drive during
this operation, it's a good idea to save any open documents
and close any other programs that may need to write to the disk
while it's being shredded. Any program that attempts to allocate
additional disk space is bound to fail, so it's better to shut
the program down beforehand than to leave it running and risk
a possible crash and/or loss of data. By the same token, it's
also a good idea to disable your screensaver and, if you are
using Power Management to put your system into "suspend"
mode after a period of "inactivity", disable that
feature as well.
IMPORTANT NOTE: unforeseen events (such as a power failure,
system crash, etc.) that occur while Shredder is shredding free
space my leave the target drive with no free space available.
To recover that free space, just delete the SHREDTMP.$$$
folder from the root directory of that drive. If you do this
with Windows Explorer, be sure to hold the Shift key down as
you execute the delete command, so that Explorer will delete
the folder outright instead of trying to send it to the Recycle
Bin. You should also use ScanDisk (Windows 9x) or CHKDSK (Windows
NT) to check the drive for errors. If either program reports
any "lost cluster chains", you should instruct the
program to delete them.
WINDOWS ME/XP USER NOTE: when Shredder allocates all
available disk space, this causes the System Restore feature
to stop monitoring. Monitoring resumes automatically when Shredder
deletes its temporary files, but the system discards all but
the most recent Restore Point .There is no way for Shredder
to prevent this from happening, so an extra warning prompt will
be presented when you use this command under Windows ME or Windows
XP.
To shred the free space on a drive, Shredder does the following:
- Creates a temporary directory, named "SHRED.$$$",
in the root directory of the selected drive. Note
that on drives formatted with the FAT12 or FAT16 file
system, the size of the drive's root directory is
fixed. If there are no "slots" available
in the root directory, this step will fail. Shredder
will be unable to process the free space on that drive
until you delete at least one file or folder from
its root directory, thus freeing up at least one "slot".
This limit does not apply to FAT32 or NTFS drives.
- Queries the system to determine how much free space
is available on the drive, and estimate how many temporary
files it must create in order to occupy all of that
space. Under some versions of Windows NT, the system
administrator may assign disk space quotas for each
user. If a quota is in effect, Shredder will only
be able to process the amount of free space available
to the current user, not necessarily the entire drive,
and will present an appropriate message when this
happens.
- Creates a series of temporary files in the SHREDTMP.$$
folder so as to allocate all available free space
left on the disk. The size of each file will be either
one gigabyte or the amount of free space left on the
drive, whichever is smaller. Note that the number
of files shown in the progress dialog is an estimate.
In most cases, Shredder will not have to create as
many files as the dialog shows. For example, if the
dialog says "Prepare temporary file 1 of 4",
Shredder may only have to create 3 files.
- During the Shredder operation, you may receive a
warning prompt from Windows that you are running low
on (or have run out of) free space on that drive.
This is normal. The message will not interfere with
Shredder operation, so you may acknowledge it whenever
you wish. You can prevent Windows from bugging you
repeatedly by not answering the "out of disk
space" prompt until Shredder has finished. If
Windows offers to run the Disk Cleanup utility for
you, decline the request. Free space will be restored
automatically when either the process is complete
or after you cancel the operation.
- If you are performing a Thorough shred, Shredder
then processes each temporary file according to the
current repeat count setting. The progress dialog's
text shows you which temporary files are being processed,
how many temporary files there are altogether (an
accurate count, since Shredder now knows exactly how
many files to process), and the pass and repeat count
for the current file. The progress bar shows the status
of the current pass for the current file. Shredding
large amounts (i.e., gigabytes) of free space, especially
with the "Thorough" option, may take
several hours to complete. You may abort the operation
at any point by clicking the Cancel button.
If you are performing a quick shred, the process is
done as soon as all of the temp files are created.
- Deletes the temporary files and SHREDTMP.$$$ directory.
Because deallocating large amounts of disk space can
take a noticeable amount of time, Shredder also displays
progress information while it is performing this cleanup.
The progress dialog's Cancel button will be
disabled during this part of the process.
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3.6.
Shred Options
The Options
tab in the main window determines how the shredder overwrites
data. All changes the user makes to the settings are saved immediately
and will not change until the user changes them.
There are two methods used in the Shredder options:
A. Quick Shred.
B. Thorough Shred.
A. Quick
Shred
This means that Shredder
will make only one pass, overwriting the data with zeroes.
This is enough to protect the user's data so that "Unerase"
utilities will not be able to recover the file, and those
who attempt to examine the disk directly using Windows-
and/or DOS- based software tools will see nothing but
zeroes in the shredded clusters. This option allows for
the fastest possible processing.
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B. Thorough Shred
Tells Shredder to
overwrite data several times using varying bit patterns,
thus preventing recovery even through the use of sophisticated
and specialized hardware.
The repeat count setting (from
1 to10) determines how many times this
thorough shred process will be repeated.
A thorough shred overwrites data in 3 passes:
| Pass1: Shredder
generates a random bit pattern 4 kilobytes (KB)
in length and overwrites the data by repeating that
pattern as needed. |
| Pass2: Shredder
inverts the pattern by flipping all the bits, and
then overwrites the data with the inverted pattern.
This ensures that each and every bit of the data
on disk gets toggled at least once. |
| Pass3: Shredder overwrites
using all randomly generated data. That is, instead
of using the same 4KB pattern over and over again,
the pattern is re-randomized each time before it
is written to the file. |
This sequence
is then repeated according to the Repeat Count
setting, which ranges from 1 to
10. Thus the data will be overwritten at least
3 times, up to as many as 30 times. A setting of 3 repeats
meets or exceeds US government standards for destroying
data stored on magnetic media. High repeat counts are
allowed in case those standards changed after shredder
was written. Naturally, the more repeats you request,
the longer the shredding will take.
The Thorough
Shred option also tells Shredder to use write-through
caching as its shreds. This ensures that all data is
written directly to disk immediately instead of being
cached in memory and written to disk latter. Therefore,
the speed of a Thorough Shred operation is limited by
the speed of your disk subsystem
Note:
Shredding very large files or large amounts of free
space may take several hours to complete.
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The Subfolder options
button in Shred Folders tab launches the dialog, which
lets you determine how Shredder will treat the subfolders of
any folders that you shred.
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4.
Conflicts with other programs
Since Shredder is designed
to literally destroy data, it operates at cross-purposes with other
utilities that are designed to protect you from this sort of damage.
Here are two specific examples of this sort of conflict, and there
may be others.
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The Norton Utilities
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| This utility package includes
a "protected Recycle Bin" feature. When installed
and active, this feature alters the way the Recycle Bin works,
including maintaining and locking its own proprietary files
in the Recycle Bin's folders. Shredder will not be able to process
the Recycle Bin properly as long as this feature is installed
and active. |
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GoBack
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This program protects your
system by making its own separate backup copies of your files
as your system operates. Shredder doesn't have access to these
backups or any information about them. Therefore, it is possible
to shred a file (even the entire Recycle Bin), but then have
that file restored from GoBack's backup. There is nothing that
Shredder can do to prevent this. If you want to ensure that
your data is completely destroyed, you must discard any backup
copies that GoBack(or any other such program) may have made.
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5.
Uninstalling Shredder
You can remove Shredder from your
system using Control Panel | Add/Remove Programs. Select Shredder's
entry in the list, and then click the Add/Remove button. Note
that Shredder must not be running when you uninstall. If it is, you
will be prompted to close all instances of Shredder before the uninstall
can proceed.
Shredder does not make any changes
to your system configuration, so there is no need to reboot the computer
after the uninstall is complete.
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