Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.misc > #4043 > unrolled thread

Deleting files

Back to article view | Back to comp.misc

Contents

  Deleting files Peter Percival <peterxpercival@hotmail.com> - 2014-07-17 13:55 +0100
    Re: Deleting files Huge <Huge@nowhere.much.invalid> - 2014-07-17 14:28 +0000
    Re: Deleting files scott@alfter.diespammersdie.us (Scott Alfter) - 2014-07-17 14:30 +0000
      Re: Deleting files Peter Percival <peterxpercival@hotmail.com> - 2014-07-17 18:09 +0100
    Re: Deleting files Adrian C <email@here.invalid> - 2014-07-17 15:30 +0100
    Re: Deleting files Rich <rich@example.invalid> - 2014-07-17 16:12 +0000
      Re: Deleting files Tim Streater <timstreater@greenbee.net> - 2014-07-17 17:58 +0100
        Re: Deleting files Richard Kettlewell <rjk@greenend.org.uk> - 2014-07-17 20:14 +0100
      Re: Deleting files Dario Niedermann <dnied@tiscali.it> - 2014-07-22 00:10 +0200
    Re: Deleting files Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-07-17 17:28 +0100
    Re: Deleting files Michael Black <et472@ncf.ca> - 2014-07-17 14:01 -0400
      Re: Deleting files Tim Streater <timstreater@greenbee.net> - 2014-07-17 19:04 +0100
    Re: Deleting files Peter Mc Donough <mcd-mail-lists@gmx.net> - 2014-07-17 21:12 +0200
      Re: Deleting files Peter Percival <peterxpercival@hotmail.com> - 2014-07-18 11:41 +0100
        Re: Deleting files Peter Mc Donough <mcd-mail-lists@gmx.net> - 2014-07-18 13:36 +0200

#4043 — Deleting files

It is my belief (and you may be quite sure I know absolutely nothing 
about the matter) that when I delete a file under Windows 7 what 
actually happens is that the space used by the file is marked as 
available for new file creation.  So the supposedly deleted file might 
hang around for sometime before it gets written over; and even then it 
might be readable because some residual magnetism (? or something) 
remains on the disk which can be read by specialised hardware or software.

So, two questions:
i) is there a file deleting program that will write random data over the 
deleted file?
ii) To take care of files already deleted but not in the thorough way 
envisaged under i), is there a free space cleaning program that will 
write random data over the free space?

I fancy ii) will take a while to run.
-- 
[Dancing is] a perpendicular expression of a horizontal desire.
        G.B. Shaw quoted in /New Statesman/, 23 March 1962

[toc] | [next] | [standalone]

#4045

On 2014-07-17, Peter Percival <peterxpercival@hotmail.com> wrote:
> It is my belief (and you may be quite sure I know absolutely nothing 
> about the matter) that when I delete a file under Windows 7 what 
> actually happens is that the space used by the file is marked as 
> available for new file creation.  So the supposedly deleted file might 
> hang around for sometime before it gets written over; and even then it 
> might be readable because some residual magnetism (? or something) 
> remains on the disk which can be read by specialised hardware or software.
>
> So, two questions:
> i) is there a file deleting program that will write random data over the 
> deleted file?
> ii) To take care of files already deleted but not in the thorough way 
> envisaged under i), is there a free space cleaning program that will 
> write random data over the free space?
>
> I fancy ii) will take a while to run.

Google "windows disk scrubber".


-- 
Today is Pungenday, the 52nd day of Confusion in the YOLD 3180
"I do not believe in revealed religion — I will have nothing to do with your
immortality; we are miserable enough in this life, without speculating on
another." Lord Byron, 1778-1824, letter to Rev. Francis Hodgson, 1811

[toc] | [prev] | [next] | [standalone]

#4046

In article <lq8h4b$6ui$1@news.albasani.net>,
Peter Percival  <peterxpercival@hotmail.com> wrote:
>i) is there a file deleting program that will write random data over the 
>deleted file?
>ii) To take care of files already deleted but not in the thorough way 
>envisaged under i), is there a free space cleaning program that will 
>write random data over the free space?

Eraser does both of these:

http://eraser.heidi.ie/

  _/_
 / v \ Scott Alfter (remove the obvious to send mail)
(IIGS( http://alfter.us/            Top-posting!
 \_^_/                              >What's the most annoying thing on Usenet?

[toc] | [prev] | [next] | [standalone]

#4055

Scott Alfter wrote:
> In article <lq8h4b$6ui$1@news.albasani.net>,
> Peter Percival  <peterxpercival@hotmail.com> wrote:
>> i) is there a file deleting program that will write random data over the
>> deleted file?
>> ii) To take care of files already deleted but not in the thorough way
>> envisaged under i), is there a free space cleaning program that will
>> write random data over the free space?
>
> Eraser does both of these:
>
> http://eraser.heidi.ie/

And it's free!  I'll try it.  Thanks.

>
>    _/_
>   / v \ Scott Alfter (remove the obvious to send mail)
> (IIGS( http://alfter.us/            Top-posting!
>   \_^_/                              >What's the most annoying thing on Usenet?
>


-- 
[Dancing is] a perpendicular expression of a horizontal desire.
        G.B. Shaw quoted in /New Statesman/, 23 March 1962

[toc] | [prev] | [next] | [standalone]

#4047

On 17/07/14 13:55, Peter Percival wrote:
> It is my belief (and you may be quite sure I know absolutely nothing
> about the matter) that when I delete a file under Windows 7 what
> actually happens is that the space used by the file is marked as
> available for new file creation.  So the supposedly deleted file might
> hang around for sometime before it gets written over

It's a fairly high chance that the file in question has already been 
accessed remotely, copied and digested by whoever you are trying to hide 
it from. So deleting it now may be a bit late.

As you admit you "know absolutely nothing about the matter", look first 
at the security setup of your computer, and your behaviour using it. 
Choose and use strong passwords & investigate using Windows 7 file 
encryption (bit-locker) for your personal items. Some things may 
actually be safer for you stored in the cloud.

Beginners are told these "deleted file" stories and overlook rather 
better safe practices - those that the media don't really excel in 
telling them about.

Well, that's a vested interest of theirs.

If we were all properly informed and made all our computers so 
hack-proof, the media wouldn't get any stories to write about!

-- 
Adrian C

[toc] | [prev] | [next] | [standalone]

#4052

Peter Percival <peterxpercival@hotmail.com> wrote:
> It is my belief (and you may be quite sure I know absolutely nothing 
> about the matter) that when I delete a file under Windows 7 what 
> actually happens is that the space used by the file is marked as 
> available for new file creation.  So the supposedly deleted file might 
> hang around for sometime before it gets written over; and even then it 
> might be readable because some residual magnetism (? or something) 
> remains on the disk which can be read by specialised hardware or software.

> So, two questions:
> i) is there a file deleting program that will write random data over the 
> deleted file?

If you were running Linux, you could use the "shred" program
(http://linux.about.com/library/cmd/blcmdl1_shred.htm).

There has to be equivalents for Windows, but as I don't do Windows, I
can't suggest anything.

> ii) To take care of files already deleted but not in the thorough way
> envisaged under i), is there a free space cleaning program that will
> write random data over the free space?

Under linux, that is a simple:
  dd if=/dev/zero of=overwrite

And waiting for it to finish, the deleteing the "overwrite" file.

Likely something exists for Windows, but see "I don't do Windows"
comment above...

> I fancy ii) will take a while to run.

Yep - with time directly proportional to the amount of free space on
your disk.

And if you have a flash disk, there is no guarantee it will overwrite
everything, due to the spare blocks most flash disks have for use in
handling wear leveling.

[toc] | [prev] | [next] | [standalone]

#4054

In article <lq8skp$ug8$4@dont-email.me>, Rich <rich@example.invalid>
wrote:

> Peter Percival <peterxpercival@hotmail.com> wrote:
> > It is my belief (and you may be quite sure I know absolutely nothing 
> > about the matter) that when I delete a file under Windows 7 what 
> > actually happens is that the space used by the file is marked as 
> > available for new file creation.  So the supposedly deleted file might 
> > hang around for sometime before it gets written over; and even then it 
> > might be readable because some residual magnetism (? or something) 
> > remains on the disk which can be read by specialised hardware or software.
> 
> > So, two questions:
> > i) is there a file deleting program that will write random data over the 
> > deleted file?
> 
> If you were running Linux, you could use the "shred" program
> (http://linux.about.com/library/cmd/blcmdl1_shred.htm).
> 
> There has to be equivalents for Windows, but as I don't do Windows, I
> can't suggest anything.

Likewise under OS X I use DragThing which adds a "Secure Delete" option
when emptying the Trash. And for zeroing empty space I can use Disk
Utility.

Recovering zeroed files on an SSD is unlikely to be possible.
Recovering zeroed files on a hard drive is thought to be possible by
examining residual magnetism at the edge of drive tracks, using what I
would imagine is sophisticated and expensive equipment. Whether this is
possible with more recent drives I'm not sure (due to tracks being
narrower). If there's an entity using that sort of kit on your disk
you're probably in trouble anyway.

-- 
"People don't buy Microsoft for quality, they buy it for compatibility
with what Bob in accounting bought last year. Trace it back - they buy
Microsoft because the IBM Selectric didn't suck much" - P Seebach, afc

[toc] | [prev] | [next] | [standalone]

#4060

Tim Streater <timstreater@greenbee.net> writes:
> Likewise under OS X I use DragThing which adds a "Secure Delete" option
> when emptying the Trash. And for zeroing empty space I can use Disk
> Utility.
>
> Recovering zeroed files on an SSD is unlikely to be possible.

I would expect the opposite.  The overwriting data is almost certain to
be written to a different physical page to the one that originally
backed the logical sector you were attempting to overwrite.  The data
you want to erase will persist inside the SSD until the containing block
is GC’d, something that could be quite a while if the rest of the block
remains live.

> Recovering zeroed files on a hard drive is thought to be possible by
> examining residual magnetism at the edge of drive tracks, using what I
> would imagine is sophisticated and expensive equipment. Whether this is
> possible with more recent drives I'm not sure (due to tracks being
> narrower). If there's an entity using that sort of kit on your disk
> you're probably in trouble anyway.

I don’t believe this has been realistic for many years now.

If you really want to keep something secret, use encryption.

-- 
http://www.greenend.org.uk/rjk/

[toc] | [prev] | [next] | [standalone]

#4073

Rich <rich@example.invalid> wrote:

> Under linux, that is a simple:
>   dd if=/dev/zero of=overwrite

I prefer:
    dd if=/dev/urandom of=overwrite

So that any possibly remaining noise floor is rendered meaningless.

-- 
Gopherhole:  gopher://retro-net.org/1/dnied/
Homepage:    http://devio.us/~ndr/  

[toc] | [prev] | [next] | [standalone]

#4053

Peter Percival <peterxpercival@hotmail.com> writes:
<snip>
> So, two questions:
> i) is there a file deleting program that will write random data over
> the deleted file?
> ii) To take care of files already deleted but not in the thorough way
> envisaged under i), is there a free space cleaning program that will
> write random data over the free space?
>
> I fancy ii) will take a while to run.

It's highly dependant on the file system being used and also on the
lower-level drivers.  Probably the worst case being the firmware that sits
between the OS and an SSD -- it breaks many of the assumptions that file
shredding and disc filling programs make.  The good ones might, I
suppose, detect this a tell you that they can't help.

-- 
Ben.

[toc] | [prev] | [next] | [standalone]

#4057

On Thu, 17 Jul 2014, Peter Percival wrote:

> It is my belief (and you may be quite sure I know absolutely nothing about 
> the matter) that when I delete a file under Windows 7 what actually happens 
> is that the space used by the file is marked as available for new file 
> creation.  So the supposedly deleted file might hang around for sometime 
> before it gets written over; and even then it might be readable because some 
> residual magnetism (? or something) remains on the disk which can be read by 
> specialised hardware or software.
>
Yes, this happens, but if you are making lots of saves, chances are the 
space will get reused fairly fast.

I remember scrambling some floppy disks, wiping out the FAT table. 
(The FAT is where the location of the starts of files is kept.) And it 
wsa a big drag to resurrect those files.  They were't necessarily in 
sequential order, so even when you found the starting point, you might 
have to leap around.  It's been a long time, most of what I remember about 
that is that it had to be pretty important to follow through on.  I dont' 
think I ever did bother resurrecting any files, too much trouble.

So if you're worried that someone might get ahold of your hard drive and 
find deleted files, that's less likely the longer you keep using that 
drive. And for someone to go to the trouble of finding deleted files, 
there has to be some incentive to do so.  Why bother with the hard drive 
of John Q. Random?  Might as well wait and find a hard drive tossed out by 
royalty or someone who might have stuff worth knowing about.

There's always a risk, but it diminishes fast.  IN everyday use, unless 
you were doing something illegal, deleted files shouldn't be an issue. 
Getting rid of the hard drive probably is worth some effort to make sure 
things are deleted, but even then there are more steps that can be taken 
if someone knows the information is worth it, while without any value 
placed on the information, nobody will bother unless they are just 
practicing.

    Michael

[toc] | [prev] | [next] | [standalone]

#4058

In article <alpine.LNX.2.02.1407171356300.1266@darkstar.example.org>,
Michael Black <et472@ncf.ca> wrote:

> On Thu, 17 Jul 2014, Peter Percival wrote:
> 
> > It is my belief (and you may be quite sure I know absolutely nothing about 
> > the matter) that when I delete a file under Windows 7 what actually happens 
> > is that the space used by the file is marked as available for new file 
> > creation.  So the supposedly deleted file might hang around for sometime 
> > before it gets written over; and even then it might be readable because
> > some 
> > residual magnetism (? or something) remains on the disk which can be read
> > by 
> > specialised hardware or software.
> >
> Yes, this happens, but if you are making lots of saves, chances are the 
> space will get reused fairly fast.
> 
> I remember scrambling some floppy disks, wiping out the FAT table. 
> (The FAT is where the location of the starts of files is kept.) And it 
> wsa a big drag to resurrect those files.  They were't necessarily in 
> sequential order, so even when you found the starting point, you might 
> have to leap around.  It's been a long time, most of what I remember about 
> that is that it had to be pretty important to follow through on.  I dont' 
> think I ever did bother resurrecting any files, too much trouble.
> 
> So if you're worried that someone might get ahold of your hard drive and 
> find deleted files, that's less likely the longer you keep using that 
> drive. And for someone to go to the trouble of finding deleted files, 
> there has to be some incentive to do so.  Why bother with the hard drive 
> of John Q. Random?  Might as well wait and find a hard drive tossed out by 
> royalty or someone who might have stuff worth knowing about.
> 
> There's always a risk, but it diminishes fast.  IN everyday use, unless 
> you were doing something illegal, deleted files shouldn't be an issue. 
> Getting rid of the hard drive probably is worth some effort to make sure 
> things are deleted, but even then there are more steps that can be taken 
> if someone knows the information is worth it, while without any value 
> placed on the information, nobody will bother unless they are just 
> practicing.

Pay no attention to this idiot. If you're getting rid of a computer, or
a hard drive, you should wipe it (format it and write zeroes
everywhere, using another computer) and then re-install the OS (if
you're selling or giving it away).

Unless of course you don't mind people seeing copies of old bills, your
credit card details or bank details, and the like.

-- 
"I am enclosing two tickets to the first night of my new play; bring a
friend.... if you have one." - GB Shaw to Churchill "Cannot possibly
attend first night, will attend second...  if there is one." - Winston
Churchill, in response.

[toc] | [prev] | [next] | [standalone]

#4059

Am 17.07.2014 14:55, schrieb Peter Percival:
> It is my belief (and you may be quite sure I know absolutely nothing
> about the matter) that when I delete a file under Windows 7 what
> actually happens is that the space used by the file is marked as
> available for new file creation.  So the supposedly deleted file might
> hang around for sometime before it gets written over; and even then it
> might be readable because some residual magnetism (? or something)
> remains on the disk which can be read by specialised hardware or software.
>
> So, two questions:
> i) is there a file deleting program that will write random data over the
> deleted file?
> ii) To take care of files already deleted but not in the thorough way
> envisaged under i), is there a free space cleaning program that will
> write random data over the free space?

There are two aspects:

Is the data confidential or secret?

If it is only confidential you simply might use an encrypted 
directory/partition which allows access while you are using it and keeps 
it at other times encrypted.

For overwriting unused space with zeros or random data you might use 
"sdelete" (for Windows) which is free.

If you intend selling a hard disk "sdelete" should be enough to prevent 
the casual snooper from accessing the data.
A professional alternative is always taking the drive apart and smashing 
the parts to pieces.

If the data is secret, protection depends on whether you have more 
resources than those who want your data.
Your chances are slim as you have no idea of how many backdoors there 
are already provided by your operating system/programs/hardware.

cu
Peter

[toc] | [prev] | [next] | [standalone]

#4062

Peter Mc Donough wrote:
> Am 17.07.2014 14:55, schrieb Peter Percival:
>> It is my belief (and you may be quite sure I know absolutely nothing
>> about the matter) that when I delete a file under Windows 7 what
>> actually happens is that the space used by the file is marked as
>> available for new file creation.  So the supposedly deleted file might
>> hang around for sometime before it gets written over; and even then it
>> might be readable because some residual magnetism (? or something)
>> remains on the disk which can be read by specialised hardware or
>> software.
>>
>> So, two questions:
>> i) is there a file deleting program that will write random data over the
>> deleted file?
>> ii) To take care of files already deleted but not in the thorough way
>> envisaged under i), is there a free space cleaning program that will
>> write random data over the free space?
>
> There are two aspects:
>
> Is the data confidential or secret?
>
> If it is only confidential you simply might use an encrypted
> directory/partition which allows access while you are using it and keeps
> it at other times encrypted.

That's fine for files I'll create tomorrow but not for those I created 
yesterday!

> For overwriting unused space with zeros or random data you might use
> "sdelete" (for Windows) which is free.
>
> If you intend selling a hard disk "sdelete" should be enough to prevent
> the casual snooper from accessing the data.
> A professional alternative is always taking the drive apart and smashing
> the parts to pieces.
>
> If the data is secret, protection depends on whether you have more
> resources than those who want your data.
> Your chances are slim as you have no idea of how many backdoors there
> are already provided by your operating system/programs/hardware.

I had wondered of the Secret Services wrote their own operating systems 
and applications, or do they just have a quiet word with Microsoft (and 
the like) along the lines of: "what you sell to everyone else will have 
the backdoors, what you sell to us won't"?

Happily, my data is just confidential rather than secret.

-- 
[Dancing is] a perpendicular expression of a horizontal desire.
        G.B. Shaw quoted in /New Statesman/, 23 March 1962

[toc] | [prev] | [next] | [standalone]

#4063

Am 18.07.2014 12:41, schrieb Peter Percival:
> Peter Mc Donough wrote:
>> Am 17.07.2014 14:55, schrieb Peter Percival:

>> If it is only confidential you simply might use an encrypted
>> directory/partition which allows access while you are using it and keeps
>> it at other times encrypted.
>
> That's fine for files I'll create tomorrow but not for those I created
> yesterday!

And the cached data nicely distributed across the hard disk.

I use Linux and "encfs" which on my computer creates an encrypted directory.
This is opened or closed via a script I start. All I want encrypted has 
been/will be  moved into that directory.
When open I don't notice any difference to other non-encrypted files. 
When closed you just see "garbage" in that directory.
Enough protection against snooping in case I have to send in the hard 
disk for repairs or someone steals the computer and the data is not the 
reason for that theft.

>> ...
>> Your chances are slim as you have no idea of how many backdoors there
>> are already provided by your operating system/programs/hardware.
>
> I had wondered of the Secret Services wrote their own operating systems
> and applications, or do they just have a quiet word with Microsoft (and
> the like) along the lines of: "what you sell to everyone else will have
> the backdoors, what you sell to us won't"?

Remember: There are unknown unknowns.
They can't be sure ;-)), Maybe they use DOS and sneaker Net.

cu
Peter

[toc] | [prev] | [standalone]

Back to top | Article view | comp.misc

csiph-web