leaving no trails

[zoran]

What ill be asking here is a little oposite to what users usually need. I want to know how can i permanently delete the files i have on OSX without leaving any chance of someone to use a retreive data application to see the files i had copied/worked and deleted on my mac.
What is the most secure way, so one cannot retreive deleted files from my hd? I know formating the drive might be one way to permanently loose data (is it?) but thats a very drastic action cause u have to kill every data on the mac and i dont want to kill apps etc. Perhaps theres an app that can do this file trails vanishing?
Some time ago in Windows (win98), if i remember correctly, when defrag was made it wasnt very easy to locate/retreive deleted files, whats the case in OSX? How can i leave no trails to the person that will use my computer after me?
Just to inform, i do not have a second partition on my hd, i only have one partition for all!

[mad jew]

You can use the Secure Empty Trash feature in Finder on specific items. This should rewrite zeroes over the where the files were written to the hard drive so that it will be more difficult to find by data recovery apps and techniques.

[zoran]

Is this a safe action? Say for eg. i have a jpg picture, if i open it in Pshop and paint it all one color and then save and replace it, is the first version retreivable by any means?

[MacNut]

The more times you write over a file the harder it is to retrieve.

The best way is to smash the hard drive platter into tiny pieces.

[mad jew]

I'm not quite sure I know what you want to do. My earlier suggestion is in reference to making sure a file you delete is difficult to find again using data recovery apps.

[MacNut]

Ya, do you want to give the computer to someone with no personal data on it, or do you just want to clear out files?

Even if you reformat the Hard Drive, the data is still there, what you want to do is wipe the drive a few times with a program that writes 1's and 0's all over the drive making it virtually impossible for it to retrieve. Then reinstall the OS.

[Blubbert]

Ya, do you want to give the computer to someone with no personal data on it, or do you just want to clear out files?

Even if you reformat the Hard Drive, the data is still there, what you want to do is wipe the drive a few times with a program that writes 1's and 0's all over the drive making it virtually impossible for it to retrieve. Then reinstall the OS.

You can use Disk Utility to wipe the disk and overwrite the disk with zeroes up to 35 times. The 35 times overwrite option takes too long though. Just using the option to overwrite the disk 7 times will make almost all data retrieval impossible.

[zoran]

You can use Disk Utility to wipe the disk and overwrite the disk with zeroes up to 35 times. The 35 times overwrite option takes too long though. Just using the option to overwrite the disk 7 times will make almost all data retrieval impossible.

Does that mean that all the data from the disk will be wiped out?

Ya, do you want to give the computer to someone with no personal data on it, or do you just want to clear out files?

Even if you reformat the Hard Drive, the data is still there, what you want to do is wipe the drive a few times with a program that writes 1's and 0's all over the drive making it virtually impossible for it to retrieve. Then reinstall the OS.

I will give my mac to someone, prolly sell it to him, so i dont want him searching and finding any of my files. On the other hand i dont want to delete any applications or system settings etc.

I guess the real question is, how can i delete trails of files i have already deleted without using the secure trash method.

[Eraserhead]

Reformat the Hard drive and reinstall OS X, while running a 7-pass erase should do it.

[zoran]

Reformat the Hard drive and reinstall OS X, while running a 7-pass erase should do it.

Reformating mean deletion of applications etc. so its not an option!

[Eraserhead]

Reformating mean deletion of applications etc. so its not an option!

You should back up your hard drive anyway in case it fails, so it shouldn't be an issue ;).

[zoran]

No the drive cannot be touched that way, it is backed up alright but i cannot be formatted due to personal reasons i cannot explain here!
So what are my options without reformating?

[iW00t]

No the drive cannot be touched that way, it is backed up alright but i cannot be formatted due to personal reasons i cannot explain here!
So what are my options without reformating?

None.

Short of reformatting there is no way to guarantee that. Especially on OSX, files get defragmented on the fly and cluster tips might contain bits of naked pictures of yourself (and other yummy stuff) that would otherwise be inaccessible for secure deletion tools.

If that data's privacy is so important to you. Wipe and reformat. If you lost the original DVDs. Warez the DVD, wipe and reformat. If it is a stolen computer with firmware lock, reset the firmware lock then wipe and reformat.

I don't care about what personal reasons you have, it smells really dodgey to me. In short you have no other choice.

[Eraserhead]

I don't care about what personal reasons you have, it smells really dodgey to me. In short you have no other choice.

It sounds like it's a stolen laptop with an Apple Firmware password on the HD so it can't be reformatted.

[zoran]

haha stolen! its not stolen. i was hoping i wouldnt have to get into explaining all this but since u called me a thief then i have to explain. well reason is that i just dont have the apps installed in dvds (and i have a lot of apps). the deal is to sell the machine with these apps, cause they are needed by the guy who will get it so i cant risk of deleting them and not beeing able to put them back in... ok now?

[mkrishnan]

If you want to securely delete traces of already deleted files, Disk Utility -> select the disk -> Erase pane -> Erase Free Space.

It has analogous options to reformatting but only impacts free space -- i.e. space in which deleted files live.

And stop with the "I can't say" and "reasons not to be discussed here" crap. It just makes you sound like you're in the kiddie porn industry. :rolleyes:™

[Amber]

Just install Windows on it. That should screw it up beyond belief.

[Eraserhead]

well reason is that i just dont have the apps installed in dvds (and i have a lot of apps). the deal is to sell the machine with these apps, cause they are needed by the guy who will get it so i cant risk of deleting them and not beeing able to put them back in... ok now?

You realise that Mac's Applications still work if you back them up? You won't have to reinstall them afterwards, or you can clone the hard drive with a program like Superduper (http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html).

EDIT: mkrishnan's advice is probably the most sensible.

[mkrishnan]

EDIT: mkrishnan's advice is probably the most sensible.

It's true. I don't lie, stay away from Kiddie Porn, people. ;)

[zoran]

Ok so for beeing secure of already deleted files i must do
Disk Utility -> select the disk -> Erase pane -> Erase Free Space
After i make the free space Erasion, does secure trash emptying cover me in the future when deleting files, or must i always do the erase free space command to be sure of a high standard safety?

[mkrishnan]

Ok so for beeing secure of already deleted files i must do
Disk Utility -> select the disk -> Erase pane -> Erase Free Space
After i make the free space Erasion, does secure trash emptying cover me in the future when deleting files, or must i always do the erase free space command to be sure of a high standard safety?

Erm... okay, you're coming up on another :rolleyes:™... :D

Why don't you just empty the trash and then do the Disk Utility Erase Free Space once before you give this person the computer? I mean, FFS...

[zoran]

Just asking so i can figure out the level of safety that the Secure Empty Trash option provides, is it like the 1st level of Free Space Erasion.

Also something else important, what is that temporary file created when erasing free space? can i delete that after cause its taking up all my hds space

[mkrishnan]

It shouldn't leave behind a temp file... it should get rid of it, itself.

As far as your question goes, the only thing I can think of is that, depending on your level of paranoia, some files get deleted without passing through the trash -- some programs, when you delete the file from inside the program, delete it immediately (e.g. when you clean the cache of Firefox or Safari, I don't think it goes to the Trash folder). So if you just secure empty trash, those files are missed. Shouldn't usually be a big deal, but based on what you said you want, erase free space is somewhat more secure.

I would do one more thing, as well. I would create another user account and then delete your user account. After you delete your user account, I'd do the secure erase. Then, anything that's hidden in your library, etc, should be gone. Files outside your user directory should not contain any private data (unless you specifically put something somewhere else outside your user folder).

[zoran]

Ok mkrishnan, great explanations from you and everybody in here thanx

Now let me ask you one more thing, hopefully. Where does it say how mutch free space is required to make a Erasion of Free Space? I have a 80gb hd with 25gb free space and a pop up msg came warning me of not enough space, so i had to move files to elsewhere!

[mkrishnan]

Now let me ask you one more thing, hopefully. Where does it say how mutch free space is required to make a Erasion of Free Space? I have a 80gb hd with 25gb free space and a pop up msg came warning me of not enough space, so i had to move files to elsewhere!

Are you using FileVault?

[zoran]

no
why do u ask?
whats that?

[mkrishnan]

no
why do u ask?
whats that?

It encrypts the home directory...I asked because I wasn't aware of this whole temp file issue with erasing free space. I don't think I've ever heard about that before.

I'll give this a try on my iBook (40GB had drive = 37GB total, 14GB available) and see what happens. If it didn't go without saying, you should NOT be *doing* anything else on your Mac while you're erasing free space... it might get confused as other programs continue to open and delete files. Anyway, I will let it finish and then tell you how much free space I have when I'm done, or if there's any change.

[zoran]

Incase im missing something, how can i check if i have the file vault set?

[mkrishnan]

Incase im missing something, how can i check if i have the file vault set?

System Prefs -> Security.

But I don't think that's it... okay, I haven't tried this secure erasing any time recently...but something strange happened to me also.

I started the secure erase, and it was working fine. It got to about 95% done, and then I got the disk full message. It kept going, but it didn't seem to go anywhere, and I couldn't hear disk activity. Ultimately, I hit the skip button. After some time, it finally finished the process, and all the free space was given back to me. In the log however, it states that it was only "89.9% complete" at the time it was stopped...

Strange, what a conundrum. How can you have more free space than you have free space? I don't see why this should ever be an issue....

I'll try it once more to see if the same thing happens.

[zoran]

dont press the skip button let it continue, i did and all finished well

[mkrishnan]

dont press the skip button let it continue, i did and all finished well

Second time I did it, it seemed to hang for quite some time near the end of the process, but no disk space warning message, and it reported success after I came back from taking a shower. Strange, huh?

[zoran]

very very strange!

[jsw]

No the drive cannot be touched that way, it is backed up alright but i cannot be formatted due to personal reasons i cannot explain here!
Reformatting and reinstalling would, using the options available then, allow you to safely install all the legal software while erasing everything else.

If the stuff isn't pirated, I apologize. But, assuming it is, I find it ironic that you're afraid of someone else stealing info from you.

Edit: I've been informed that the software media is at home and that the system will be sold without media and with the media staying with zoran, which is counter to most licenses.

This is advocation of illegal activity and will be Wastelanded.