how to make sure a permanently delete file (shift+delete) has been deleted and is not recoverable with advanced software

Question

Hi experts, I have been cleaning my hard disk using shift delete as well as normal delete and then empty recycle bin. I am doing this so I can prepare it to be sold on if I find a moment (and a buyer).

I am told however, that this actually does not delete any files but just marks them as 'over-writeable'. And that it takes some time - depending on how much has been marked to be permanently deleted - for those files to be over-written.

How do I ensure all those files that I wish to permanently delete are not even recoverable with advanced software?

How long would it take to over-write say 20GB of data?

Your advice is much appreciated.

Rgds,

WV

Answer 1

Use Google or Bing to search for "file shredder" or "secure erase" software that will overwrite files with random patterns of data, making them unrecoverable by most efforts.  HOWEVER, please do keep in mind that no matter what you do, short of physically destroying the hard drive, there will always be ways to recover files even if those files were wiped securely.  That would be why US Federal agencies that require high security have their hard drives shredded into metal fragments when they dispose of computers.

Answer 2

Data can be recovered but you can bet if it is a file you want you will be out of luck.

Have a look at this web page :-

http://www.techrepublic.com/blog/five-apps/five-hard-disk-cleaning-and-erasing-tools/1568

Answer 3

Thank you both for your quick replies.

Will a file shredder also take care of files that I have already permenently deleted or will it only work for files that I delete using such tool?

Also keen to know about over-writing deleted files and how long this would typically take.

Thanks in advance!

WV

Answer 4

It only works for files on which it has been specifically used.

So,

1. who else has access to your computer?
2. Does it have a second hard drive?
3. Does anybody with access to your computer have a large flash drive?
4. Is your computer left unguarded for hours in a place where somebody is likely to try to recover deleted files?
5. Do you have sensitive stuff on your PC that is a threat to you or National Security?

It takes hours for a file recovery utility to scan a hard drive, and it needs to deposit what it has found to another physical drive.

Unlike TV and movies, it is NOT a one click process, results are anything but guaranteed, and the files recovered will NOT all fit on one floppy disk. For the purposes of solving crimes, only small bits of evidence are required which is more often what one gets after running a file recovery process.

How long does it take for files to be overwritten? That depends on how much files are written to the areas where the previous files were stored.

Sometimes it is this long <..................> and sometimes it is this long <.............................................>

Answer 5

Thanks for clarifying. As mentioned, I will be selling the laptop and just don't want the buyer to be able to access my personal info after having supposedly permanently deleted it from the disk as described above.

In answer to your questions:

1. the buyer
2. not that I am aware of
3. possibly
4. n/a
5. no, just personal files and pics and such like

Rgds,

WV