data is never truly erased?

[JeremysFilms]

I've heard many times that data is never truly erased from a computer. Like if a file is deleted, it's never completely gone. Would someone please explain why and how this happens. And what is the solution to fully remove data?

[authorblues]

At 12/29/06 10:53 PM, JeremysFilms wrote: I've heard many times that data is never truly erased from a computer. Like if a file is deleted, it's never completely gone. Would someone please explain why and how this happens. And what is the solution to fully remove data?

thats just in windows, as far as i know...
http://computer.howstuffworks.com/question578 .htm

[thoughtpolice]

At 12/29/06 11:20 PM, authorblues wrote: thats just in windows, as far as i know...

No, no matter how pessemistic the UNIX rm man page is, data can generally linger on just about any type of disk and any type of file system for very long periods of time (it's really more filesystem dependent than it is operating system dependent.) If you want to read into the subject some, you can read up on something called the "Guttmann Method" and the papers on the subject the author of that method have written.

[RageOfOrder]

With any file system, when a file is deleted, the data is still there until something overwrites it.

With the common unix filesystems (ext2/3, ReiserFS, JFS) you have inodes that point at the data on the disk. When you delete something, you just delete the inodes, or the pointers to the data, and so that space in memory where the "deleted" data is held, is treated as empty, and eventually gets overwritten with something new.

So the quick answer is the only way to delete a file is to overwrite it with something else.

[smulse]

At 12/30/06 12:36 AM, RageOfOrder wrote: So the quick answer is the only way to delete a file is to overwrite it with something else.

Yeah, say you had a file "bla.txt" and you wanted to safely remove it, delete all it's contents and write something else in there several times to make sure that it's gone and been overwritten. Or you could always buy the strongest magnet you could off eBay and drag it around the surgace of your HDD, although that'd do more than just remove that one file.

[RageOfOrder]

Safe deletion pretty much involves a program that fetches the actual location in memory where your data is stored, and overwrites it with say, all 0's. It may do this multiple times, then shuffle up the file and do it again, and THEN delete the inodes (pointers) to it, so even if you try to recover the memory, it's all been overwritten first, and all you'll find is 0's

[thoughtpolice]

At 12/30/06 03:42 PM, RageOfOrder wrote: Safe deletion pretty much involves a program that fetches the actual location in memory where your data is stored, and overwrites it with say, all 0's. It may do this multiple times, then shuffle up the file and do it again, and THEN delete the inodes (pointers) to it, so even if you try to recover the memory, it's all been overwritten first, and all you'll find is 0's

Technically, it's still pretty reasonable to still find traces of the data or reconstruct it, the Gutmann Method is an attempt to overwrite your data with a very meticulously chosen set of bit patterns multiple times (although Gutmann himself admits the Gutmann method isn't the best option,) he wrote a paper on the subject if you want to read it (it's a hard read) here

[dELtaluca]

even if you do overwrite it with zeros, doesnt it leave a magnetic trace on the disc that can be recovered?

[GustTheASGuy]

At 12/30/06 07:33 PM, dELtaluca wrote: even if you do overwrite it with zeros, doesnt it leave a magnetic trace on the disc that can be recovered?

What should really concern you is that in the future there'll be a way neutrino particles can be focused and read thus making anyone capable of tracing anything that ever happened to the chip even after someone came to the rescue with a mallet!

[PONGpaddle]

You guys are thinking in terms of computing.

Think thermite.

[THEBIPOLARGOD]

Nope never goes away. Wheres it gonna go? It may get it off your components but not off your drive. Only magnets can completley destroy computed files.

[Disarray-yarrasiD]

Use BC wipe.

its free software that can delete the "free space" on your computer. I believe that it replaces it with some sort of text document then deletes the reference to the text document.