Do You Swear by "Secure Empty Trash"? Why?

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sonofsylvanussonofsylvanus
Posted:
in macOS edited January 2014
Do fragments of data that have been deleted normally, rather than with Secure Empty Trash, stay with you Forever?



Say, even if you moved your Home volume to a new computer, would there still be fragments of deleted applications, folders and files that would handicap your system from the start?



How, if at all, can these fragments be reconstructed or re-located, then deleted properly? What kind of software would do this?



I am Secure Emptying my Trash at the moment but it is taking ages. I normally don't bother (1 hour or so - 30 files deleted...)

Comments

  • Reply 1 of 17
    sledgehammersledgehammer Posts: 505member
    I didn't even realize there was a secure empty trash option now. That's pretty cool. If I ever had anything I felt that I needed to trash for good, I'd use Stuffit's Secure Delete.
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  • Reply 2 of 17
    stupider...likeafoxstupider...likeafox Posts: 1,618member
    OK, both of you seem confused.



    A) Secure Delete will provide no performance benefit, it is included for people who work for the government and paranoiacs so that they can 'shred' digital documents. (Whether this actually works in practice or not is an interesting question.)



    B) Secure Delete is built into the OS from Panther onwards. I have no idea what Stuffit's Secure Delete is but if it's as poor as everything else they do I'd avoid it. (edit: I see what you're saying now, you used to use Stuffit's because you didn't know it had been added to Panther. I'd trust the Stuffit version even less than the Apple one if there's something that I really didn't want people to find though.)
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  • Reply 3 of 17
    baumanbauman Posts: 1,248member
    To understand how deleting files works, you need to know a bit about how file systems work.



    All of your documents are simply 1 and 0s scattered across your hard drive... and the way the computer knows how to retrieve it is by a database that tracks where on the hard drive your data is. When you delete normally, it is simply the pointer to your data that gets erased. The 1s and 0s are still there, but the operating system thinks of it as free space since it doesn't know that anything is there.



    So, in time, it will probably be written over with more documents. But there are utilities that can specifically look for this kind of stuff and retrieve it if you haven't overwritten it yet. And if you copy your home folder to another drive, only the data that the OS knows about would be copied... nothing that has been deleted would be transfered. Actually, when you copy your entire hard drive, it is de-fragmented at the same time since it copies one entire file at a time - so the source sends entire files intact, and the destination drive writes it continuously.



    Secure delete, on the other hand, actually overwrites your data (several times?) so that way there is absolutely no remnant left on the hard drive.
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  • Reply 4 of 17
    scottscott Posts: 7,431member
    It stalled out for me. rm -P seems to work much faster.
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  • Reply 5 of 17
    ghost_user_nameghost_user_name Posts: 22,667member
    Since this is specifically a Mac OS X 10.3+ feature, I'm moving this thread to the Mac OS X forum.
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  • Reply 6 of 17
    sonofsylvanussonofsylvanus Posts: 579member
    Thanks bauman. Me understandie now
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  • Reply 7 of 17
    nebagakidnebagakid Posts: 2,692member
    I bet it is great for getting rid of all that porn on your computer



    oh



    excuse me





    prOn... sorry
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  • Reply 8 of 17
    pbpb Posts: 4,255member
    Quote:

    Originally posted by Scott

    It stalled out for me. rm -P seems to work much faster.



    Hmm, I wonder, do rm -P and Panther's secure delete are the same thing?
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  • Reply 9 of 17
    bartobarto Posts: 2,246member
    Panther's Secure Empty Trash uses srm, not rm -P.



    srm is a dedicated program, with a lot more options (like specifying the number of passes, as was seen in the Panther alpha builds) plus on top of overwriting files, it renames and truncates them.



    Barto
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  • Reply 10 of 17
    pbpb Posts: 4,255member
    Quote:

    Originally posted by Barto

    srm is a dedicated program, with a lot more options (like specifying the number of passes, as was seen in the Panther alpha builds) plus on top of overwriting files, it renames and truncates them.

    Barto



    Thanks Barto. I just installed it (via fink) and the only option I see for the number of passes is to overwrite with a single pass. Where are the other options? It is version 1.2.6.
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  • Reply 11 of 17
    scottscott Posts: 7,431member
    srm is in the OS X install. It does have nicer features than rm -F but ... how "gone" do your files have to be?
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  • Reply 12 of 17
    pbpb Posts: 4,255member
    Quote:

    Originally posted by Scott

    srm is in the OS X install.



    Could not find it under Jaguar, that's why I installed it using fink. You mean perhaps Panther?
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  • Reply 13 of 17
    scottscott Posts: 7,431member
    Yea. I specifically left off Panther/Jaguar because I didn't know. It is in Panther.
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  • Reply 14 of 17
    bartobarto Posts: 2,246member
    Quote:

    Originally posted by Scott

    srm is in the OS X install. It does have nicer features than rm -F but ... how "gone" do your files have to be?



    Yeah I mean it's not that big a deal if your computer gets stolen and someone recovers your credit cards and social security details by using Norton's Undelete.



    Oh wait, yes it is
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  • Reply 15 of 17
    scottscott Posts: 7,431member
    Quote:

    Originally posted by Barto

    Yeah I mean it's not that big a deal if your computer gets stolen and someone recovers your credit cards and social security details by using Norton's Undelete.



    Oh wait, yes it is



    I'm sorry the option is '-P'. From the man page.



    Code:


    -P Overwrite regular files before deleting them. Files are

    overwritten three times, first with the byte pattern 0xff,

    then 0x00, and then 0xff again, before they are deleted.









    Where as srm has options to write random data and other stuff.



    Code:




    -s, --simple

    only overwrite with a single pass of random data



    -m, --medium

    overwrite the file with 7 US DoD compliant passes (0xF6, 0x00,

    0xFF, random, 0x00, 0xFF, random)



    -z, --zero

    after overwriting, zero blocks used by file









    So I ask again. How "gone" does the data have to be?
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  • Reply 16 of 17
    giantgiant Posts: 6,041member
    My understanding is that in order for the data to truly be unrecoverable, you need quite a large number of passes (30+) with various patterns of data written. Personally, I've used pgp for a while.



    The other issue is if any of that data gets put in the swap space on the hard drive. I believe you can get an encrypted swap with linux.
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  • Reply 17 of 17
    talksense101talksense101 Posts: 1,738member
    Quote:

    Originally posted by giant

    The other issue is if any of that data gets put in the swap space on the hard drive. I believe you can get an encrypted swap with linux.



    Does Panther's encryption allow us to have encrypted swap files? It is a intresting point that the swap file needs to be encrypted as well.
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