Shredding deleted files

On 15 Jun 2009 23:40:33 GMT, Arno wrote:

Mark F wrote:
On 14 Jun 2009 18:25:51 GMT, Arno wrote:

Arno wrote:
Mark F wrote:
On Sat, 13 Jun 2009 00:28:59 +1000, Barry OGrady
wrote in part:

On Fri, 13 Mar 2009 15:47:37 -0700 (PDT), wrote:

Do you know a program that accesses deleted files and shreddes them
once and for all? Thanks in advance!

Run a defragmenter that erases free space.
This solves the original poster's problem, but does not solve
the more basic need, which is for a program that
automatically erases files when they leave the Recycle Bin or are
deleted without going to the Recycle Bin.

AJC Software's Active Backup monitors all files so it
can save changed information, so there must be an operating system
hook that would allow handling what to do when a file is deleted
most of the time,

Not necessarily. It could just crawl the directoory structure slowly
and keep its own database to compare.
I use AJC Active Backup and I can tell it is "watching", not walking.

Well, watching and walking are the same things here.

In particular, programs that open and close many files or try to
protect their databases from crashes (such as Forte's Agent
newsreader) cause AJC Active Backup to use lots of CPU time.

This could be checksum calculations.
As soon a file is open for write it goes onto a visible queue of files
needing to be backedup. As soon as the file is closed the file starts
to be backedup (assuming it is first in the queue) "backing up" means
making a new base backup file or merging the changes with the existing
base+changes file. All this can be seen by using a system monitoring
program to see what files are being read and written on the system.

Also, although I haven't found documentation for the call to set
things up, now that I looked again I did find:
http://support.microsoft.com/kb/300605:
"How To Monitor Win32 File System Changes in Java"
says it part:
"This article describes how you can use the Win32
FindFirstChangeNotification function and its related functions to
monitor file system changes from an application."
which is at least approximately the functionality needed from the
operating system (if you don't want to muck around with patching
the actual Windows code.)


Sorry, not conclusive.

but a direct trap for file deletes would be better.

Indedd. However not ewven Unix/Linux does have such a hook,
so I expect there will be none on MS stuff.

Without a hook, I think the only thing that can reasonably be done
is a periodic (slow) overwrite of all free space.

Arno

P.S.: The real solution is, of course, to encrypt your drive.
No - I don't even want someone with the key to the encrypted disk
to get access to the deleted stuff.

(I'm sending an email to the AJC Software guys to see if they
can do write a program to erase files that are deleted.)

Good idea.

Arno

On Tue, 16 Jun 2009 13:55:51 -0400, Mark F
wrote:

On 15 Jun 2009 23:40:33 GMT, Arno wrote:

Mark F wrote:
On 14 Jun 2009 18:25:51 GMT, Arno wrote:

Arno wrote:
Mark F wrote:
On Sat, 13 Jun 2009 00:28:59 +1000, Barry OGrady
wrote in part:

On Fri, 13 Mar 2009 15:47:37 -0700 (PDT), wrote:

Do you know a program that accesses deleted files and shreddes them
once and for all? Thanks in advance!

Run a defragmenter that erases free space.
This solves the original poster's problem, but does not solve
the more basic need, which is for a program that
automatically erases files when they leave the Recycle Bin or are
deleted without going to the Recycle Bin.

AJC Software's Active Backup monitors all files so it
can save changed information, so there must be an operating system
hook that would allow handling what to do when a file is deleted
most of the time,

Not necessarily. It could just crawl the directoory structure slowly
and keep its own database to compare.
I use AJC Active Backup and I can tell it is "watching", not walking.

Well, watching and walking are the same things here.

In particular, programs that open and close many files or try to
protect their databases from crashes (such as Forte's Agent
newsreader) cause AJC Active Backup to use lots of CPU time.

This could be checksum calculations.
As soon a file is open for write it goes onto a visible queue of files
needing to be backedup. As soon as the file is closed the file starts
to be backedup (assuming it is first in the queue) "backing up" means
making a new base backup file or merging the changes with the existing
base+changes file. All this can be seen by using a system monitoring
program to see what files are being read and written on the system.

Also, although I haven't found documentation for the call to set
things up, now that I looked again I did find:
http://support.microsoft.com/kb/300605:
"How To Monitor Win32 File System Changes in Java"
says it part:
"This article describes how you can use the Win32
FindFirstChangeNotification function and its related functions to
monitor file system changes from an application."
which is at least approximately the functionality needed from the
operating system (if you don't want to muck around with patching
the actual Windows code.)
Found it:
http://msdn.microsoft.com/en-us/library/aa364417.aspx
FindFirstChangeNotification Function
which says in part:
"Creates a change notification handle and sets up initial change
notification filter conditions. A wait on a notification handle
succeeds when a change matching the filter conditions occurs in the
specified directory or subtree."
Although for writes to a file an event doesn't happen until there
is a write to a disk, I assume that it is possible to force buffer
flushing. This would cause the backup program to keep getting
awakened even when there is nothing that it can actually do,
which explains the high CPU use of the backup program when
certain other programs are operating.



Sorry, not conclusive.

but a direct trap for file deletes would be better.

Indedd. However not ewven Unix/Linux does have such a hook,
so I expect there will be none on MS stuff.

Without a hook, I think the only thing that can reasonably be done
is a periodic (slow) overwrite of all free space.

Arno

P.S.: The real solution is, of course, to encrypt your drive.
No - I don't even want someone with the key to the encrypted disk
to get access to the deleted stuff.

(I'm sending an email to the AJC Software guys to see if they
can do write a program to erase files that are deleted.)

Good idea.

Arno

Mark F wrote:
On 15 Jun 2009 23:40:33 GMT, Arno wrote:

Mark F wrote:
On 14 Jun 2009 18:25:51 GMT, Arno wrote:

Arno wrote:
Mark F wrote:
On Sat, 13 Jun 2009 00:28:59 +1000, Barry OGrady
wrote in part:

On Fri, 13 Mar 2009 15:47:37 -0700 (PDT), wrote:

Do you know a program that accesses deleted files and shreddes them
once and for all? Thanks in advance!

Run a defragmenter that erases free space.
This solves the original poster's problem, but does not solve
the more basic need, which is for a program that
automatically erases files when they leave the Recycle Bin or are
deleted without going to the Recycle Bin.

AJC Software's Active Backup monitors all files so it
can save changed information, so there must be an operating system
hook that would allow handling what to do when a file is deleted
most of the time,

Not necessarily. It could just crawl the directoory structure slowly
and keep its own database to compare.
I use AJC Active Backup and I can tell it is "watching", not walking.

Well, watching and walking are the same things here.

In particular, programs that open and close many files or try to
protect their databases from crashes (such as Forte's Agent
newsreader) cause AJC Active Backup to use lots of CPU time.

This could be checksum calculations.
As soon a file is open for write it goes onto a visible queue of files
needing to be backedup. As soon as the file is closed the file starts
to be backedup (assuming it is first in the queue) "backing up" means
making a new base backup file or merging the changes with the existing
base+changes file. All this can be seen by using a system monitoring
program to see what files are being read and written on the system.

Also, although I haven't found documentation for the call to set
things up, now that I looked again I did find:
http://support.microsoft.com/kb/300605:
"How To Monitor Win32 File System Changes in Java"
says it part:
"This article describes how you can use the Win32
FindFirstChangeNotification function and its related functions to
monitor file system changes from an application."
which is at least approximately the functionality needed from the
operating system (if you don't want to muck around with patching
the actual Windows code.)

Ok, _that_ is conclusive.

Arno