Delete files and defrag

[Francis Asis]

Is it true that if you delete files from your PC and then defrag the disc it makes it impossible to recover the deleted files?

[d0gsb0dy]

No. An experienced geek could recover the files. There are special programmes available to totally remove all trace of files, but I've had no experience of them.

[Loosehead]

When a file is deleted all that happens is that the directory is updated so that the space it used is marked as free, ie usable. At this stage then the file can be recovered. If you do a lot of disc activity then that makes it more and more likely that the file will not be recoverable. A defrag completely rewrites all the data and the directory so yes it is all but impossible to retrieve. There are techniques for looking at the ghost magnetic signature, I think that is probably what Dogsbody is referring to. But to recover from that is patchy, painstaking, time consuming and only likely to be attempted by MI5! As dogsbody says though there are industrial strength deleters that will just overwrite the disc enough times to make it impossible even for MI5.

So to answer you question, for all practical purposes defrag will make it impossible for mere mortals to retrieve deleted files.

[LeMarchand]

Dependant on what you have been up to, a defrag may only overwrite the data once. You need to get a "shredder" that overwrites the file multiple times with pseudorandom data.

Spybot contains a "Secure Shredder" if you look at it in "advanced" mode - I'm not sure how good this is. Eraser ( http://www.heidi.ie/eraser/download.php ) is a well-regarded (and free) shredder that uses US DoD standards. However, many people still recommend physically destroying the HDD just to be sure!

You may also want to Google "PC security" or similar and do a lot of reading - whilst shredding may delete the file there still may be references to it in various places on your computer (recently used documents, for instance).

[Francis Asis]

Thank you all

It wasn't something I was planning to do - someone said it on Neighbours yesterday and I wondered if it was true.

Thanks again