Deleting files from a hard drive
Deleting files from a hard drive
I have work PCs that will be passed on to colleagues in other offices. The colleagues will need the installed programmes and most date on the PCs, but there's some sensitive data that must be erased permanently with zero chance of possible recovery. Is there any programme or app out there that can target specific words (like a customer's name or a case reference) and deleting associated files , like downloaded emails or word/excel files containing those words ? I know it exists for entire hard drives but that's the nuke option, I need a more selective approach
You don't mention the filesystem but you mention Word and Excel files so I'm going to assume that you are talking about an NTFS drive mounted on Windows.
Easily explained, NTFS works with fragments and journaling saving data all over the drive. There is no selective delete. NTFS marks sections of a drive to indicate that they are ready to be overwritten. The data remains and that's why data recovery is possible after an accidental deletion.
Your only option to safely wipe the drive is to delete the partitions on it and then format the drive with a partition which is 100% of the size. Do it multiple times if it makes you feel better, it doesn't make it safer in practice. Avoid so called quick format options.
Bless
Easily explained, NTFS works with fragments and journaling saving data all over the drive. There is no selective delete. NTFS marks sections of a drive to indicate that they are ready to be overwritten. The data remains and that's why data recovery is possible after an accidental deletion.
Your only option to safely wipe the drive is to delete the partitions on it and then format the drive with a partition which is 100% of the size. Do it multiple times if it makes you feel better, it doesn't make it safer in practice. Avoid so called quick format options.
Bless
thank you Alexandra, you are right in your assumptions.
What programme would you suggest to
- transfer the files and programmes needed to an external drive
- wipe and reformat the hard drive
- put the transferred files & programmes back on the hard drive
It looks simple enough using windows backup & recovery but is there a possibility that the strings meant for deletion would be part of the backup ?
What programme would you suggest to
- transfer the files and programmes needed to an external drive
- wipe and reformat the hard drive
- put the transferred files & programmes back on the hard drive
It looks simple enough using windows backup & recovery but is there a possibility that the strings meant for deletion would be part of the backup ?
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Yes, depending on how certain programs store certain data there may be junk included in data directories that you wouldn't want to transfer.logos wrote:It looks simple enough using windows backup & recovery but is there a possibility that the strings meant for deletion would be part of the backup ?
Unfortunately I would say re-installing those programs is the best way to go to avoid such risks.
Bless
I think an old software piece "recovermyfiles" is still going; I used to use it exactly for that- recovering files from even formatted drives.
I believe however it also had a proper permanent deletion function. Also in the small print somewhere I recall reading that reformatting (full not fast as Alexandra stated) the drive beyond 7 times makes file recovery nearly impossible. Go for ten
I believe however it also had a proper permanent deletion function. Also in the small print somewhere I recall reading that reformatting (full not fast as Alexandra stated) the drive beyond 7 times makes file recovery nearly impossible. Go for ten
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ut sint Guinness proxima morientis ori.
tunc cantabunt letius angelorum chori:
"Sit Deus propitius huic potatori."
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tunc cantabunt letius angelorum chori:
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The Great Zero Challenge promised large rewards to anyone who could recover data from a drive nulled only once. The challenge remained unaccepted by large data recovery firms.
If you can restore data from a nulled drive you'll make major progress in digital forensics and winning small awards will be the least of your problems. https://m.slashdot.org/story/106639
The sad reality is that the reason why you could restore files was because they had not been removed in the first place.
Bless
If you can restore data from a nulled drive you'll make major progress in digital forensics and winning small awards will be the least of your problems. https://m.slashdot.org/story/106639
The sad reality is that the reason why you could restore files was because they had not been removed in the first place.
Bless
There's an app called file shredder will get rid of files on an NTFS filesystem.
http://www.fileshredder.org/
If you want to get rid of an entire hard drive and are comfortable at a linux command line, boot linux from a DVD and run the "shred" command. It will need arguments, but you can look that up.
I know you can shred partitions or entire drives with shred. I suspect you can shred files with it too.
http://www.fileshredder.org/
If you want to get rid of an entire hard drive and are comfortable at a linux command line, boot linux from a DVD and run the "shred" command. It will need arguments, but you can look that up.
I know you can shred partitions or entire drives with shred. I suspect you can shred files with it too.
Touched by His Noodly Appendage
-zuvf is nice.Kpal wrote:If you want to get rid of an entire hard drive and are comfortable at a linux command line, boot linux from a DVD and run the "shred" command. It will need arguments, but you can look that up.
NTFS still has a journal.
Bless
I was under the impression that programs with "secure delete" options would not just delete from the filesystem but would actually locate the space on the drive where the data was located and then overwrite it?
With the comments about recovering data or not from a reformatted drive it's important to differentiate the typical quick format which erases leaves the data there and a proper "long" format that, I believe, writes zeros across the disk and takes hours.
With the comments about recovering data or not from a reformatted drive it's important to differentiate the typical quick format which erases leaves the data there and a proper "long" format that, I believe, writes zeros across the disk and takes hours.
Allegedly, yes. If somebody wrote a program which performed an ordinary delete and claimed it was secure, could you tell the difference?1984 wrote:I was under the impression that programs with "secure delete" options would not just delete from the filesystem but would actually locate the space on the drive where the data was located and then overwrite it?
The only way to know with these programs is by disassembling them. Reverse engineers typically don't bother because they don't rely on such software to delete things securely.
Even if a program did locate the physical sectors a file is on and overwrote them, that may still not be enough. Journaling filesystems like NTFS write operations to the journal to allow recovery in case of unexpected data loss. This creates data duplicity in the journal which may contain sensitive information which a user was under the impression had been securely deleted.
NTFS journals can be deleted, Linux livecds can be booted and followed by shred and all available space of a drive can be cleaned with dd if=/dev/null, and when the OP messes up and deletes more data than he intended or sensitive data which he wanted gone remained and was recovered it will be our fault for giving him advice that went over his head. I prefer giving advice which is easy to follow to laymen and has the intended results, and in my point of view the easiest and most reliable way to solve this problem is to follow the advice I originally gave.
As for the possibility to recover data that has been properly deleted (overwritten), that is a myth that stems from a 1996 research paper called Secure Deletion of Data from Magnetic and Solid-State Memory. The myth is spread by people who have not read the paper or did not understand that those techniques applied to 30+ year old technology at the time the paper was written. Quoting Peter Gutmann, the author, himself (emphasis added):
The US government standardized voodoo deletion via its data erasure policies like DoD 5220.22-M, which many of these "secure delete" programs follow. They also melt drives that have been used to store data of the highest level of confidentiality. That doesn't mean that it's necessary, or that logos needs to throw his drive in lava.In the time since this paper was published, some people have treated the 35-pass overwrite technique described in it more as a kind of voodoo incantation to banish evil spirits than the result of a technical analysis of drive encoding techniques. As a result, they advocate applying the voodoo to PRML and EPRML drives even though it will have no more effect than a simple scrubbing with random data. In fact performing the full 35-pass overwrite is pointless for any drive since it targets a blend of scenarios involving all types of (normally-used) encoding technology, which covers everything back to 30+-year-old MFM methods (if you don't understand that statement, re-read the paper). If you're using a drive which uses encoding technology X, you only need to perform the passes specific to X, and you never need to perform all 35 passes. For any modern PRML/EPRML drive, a few passes of random scrubbing is the best you can do. As the paper says, "A good scrubbing with random data will do about as well as can be expected". This was true in 1996, and is still true now.
As a matter of fact, nobody has ever recovered data from a modern drive that has been properly overwritten only once. There is a lot of hocus pocus told by data recovery firms and echoed by people who have not done their research or ever tried to perform data recovery themselves.
There are many misunderstandings. Apologies if I sound like a total besserwisser.
Bless
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