Secure Data Disposal
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Time
35 hours 25 minutes
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Advanced
Video Transcription
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>> We've just discussed legal considerations,
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and now we're going to move into
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discussing secure data disposal.
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Often we're concerned with protecting
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data at rest or in transit,
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but we have to remember at the end of data's life cycle,
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it still may be valuable to
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>> attackers or other entities.
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>> We have to make sure that we remove
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data from its location if it still has value.
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We'll talk about some of the ways that we sanitize
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our media to make sure we have removed all of our data.
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Now, how we sanitize
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our media is going to be driven
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by the type of media we have.
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We may have magnetic media,
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we may have paper media,
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we may have non-magnetic storage.
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Ultimately we have to figure out,
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in a lot of times our classification strategy.
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Well, not a lot of times our classification strategy
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should dictate based on the value of the data,
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how it's to be disposed.
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For instance, with top-secret data,
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I can't just delete a file,
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and reuse the disk.
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I have to destroy the disk in which it was stored.
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We need this to be part of
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our classification strategy as well,
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and we consider the classification of data,
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the type of media,
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where the media is located,
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how much media there is to sanitize,
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what type of availability
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we have for tools and equipment.
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Several strategies and this
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just gives you that visual idea.
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Now the strategies that we have,
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we have clearing, purging, and destruction.
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Quite honestly, a lot of people will
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use these terms interchangeably,
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but technically they do have different meanings.
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The first is called clearing.
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That's the same as overwriting a disc.
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Sometimes you'll hear people talk
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about the zeroization of a drive.
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Which means we're going to take this drive,
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and we're going to overwrite,
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ones and zeros or just zeros, just ones.
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We're going to overwrite the data.
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We're generally going to do that multiple times so that
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the data is inaccessible by normal means.
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Meaning most casual attackers,
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I'll say casual attackers,
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are not going to be able to access
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the data using traditional equipment.
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Now, depending on how many times your zeroize was,
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or you clear the drive,
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you're going to make it incredibly
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difficult to retrieve that data.
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Some software zeroizes
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the drive three times, some seven times.
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However, it has been proven that,
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in the case of high-end forensic tools,
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data can still be
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retrieved by an electron microscope that's been
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zeroized on a disk 16 times, that's pretty significant.
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Even stronger than clearing is purging.
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Not only are we rendering the data inaccessible,
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we're actually rendering the media inaccessible.
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What we used to do when we primarily
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had hard drives that stored using magnetic means,
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is we would degauss those drives.
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The way magnetic hard drives work
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is they're made up of a series of disks,
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and on those disks magnetically created,
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there are cylinders, tracks, and sectors.
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That's how data is stored.
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Well, when we degauss,
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we expose that drive to a very strong magnet,
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and we actually remove the cylinders,
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the tracks, and the sectors.
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The drive becomes unusable by normal means.
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Now technically though, you could reuse that drive
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by conducting what's called a low-level format.
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Low-level formats are not common
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today, they take a lot of time,
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and even though you could recover the cylinders,
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tracks, and sectors, you're almost
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assuredly not going to be able to access the data.
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But two problems with that.
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First problem is that today,
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a lot of the hard drives we're using
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our solid state devices, SSDs.
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Those do not use magnetic storage,
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and they are not going to be susceptible to degaussing.
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Those are much more like RAM, and really,
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you either need to physically destroy
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those devices or often the disk will come
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with not a degaussing but
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a true eraser program
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that you could use to remove your data remnants,
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but degaussing has no effect on a solid state disk.
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The other issue is that,
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of the utmost sensitive material,
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that's still not a strong enough assurance
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that all remnants are removed.
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Now, I'm not talking about your grocery list,
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I'm talking about top-secret data.
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If we've got top-secret data,
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data of a national importance
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with grave danger if it were harmed,
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then we would really
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only be able to choose in that instance,
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physical destruction, and
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I mean true physical destruction.
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I don't mean putting a nail through drive because that
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just renders a small portion of the drive unavailable.
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What I mean, is shredding, pulverizing.
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If we're talking about paper,
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using chemical to remove the ink from the paper,
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pulping it, making sure that
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it's truly physically destroyed.
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Then the other technique that I mentioned a
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bit earlier was crypto-shredding
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for drives that you don't have physical access to
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encrypting the data with
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a strong publicly known algorithm
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then destroying the key.
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We can't forget that throughout the data life cycle,
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we provide protection for the data,
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we can't forget at the end of its life,
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it has to be treated with secure practices as well.
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We can think about clearing, purging,
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and physical destruction as
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good means of protecting our data,
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and making sure there are no remnants left behind.
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