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- In this lesson 4.6,

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we're gonna be talking
about Steganography.

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Now, steganography isn't
really a cryptographic solution

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but because it hides data,
that's its goal, right?

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It makes data unreadable,

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this seemed like the
logical place to add it.

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So it's in this lesson with us.

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So steganography is the
science of hiding information.

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Now it consists of a
message and a cover image.

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The message is the secret data,

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the cover image is the carrier
that hides the message.

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You may have seen examples of this

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in maybe some murder mysteries
that you've read or watched.

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Steganalysis is the study of detecting

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those hidden messages using steganography.

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So what might be some of
those digital cover images?

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Well, we might embed the message in text

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hiding information in a text file.

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Maybe every nth letter,
or on every nth page.

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Could be in an image.

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Hiding information in an image file

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like a BMP or a JPEG
or a GIF or a PNG file.

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In audio, hiding
information in an audio file

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like a WAV or an AU or an MP3.

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Or hiding information in a video file

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like an AVI or an MP4 or an MPEG.

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Those are all of the covers,

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we put the message inside those covers

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to hide the message.

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The objective of
steganography is concealment

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and there's a variety of use cases.

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For example, a digital watermark
is really a hidden message

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that's used to prove or claim ownership,

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generally of intellectual property

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or an artistic work.

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So that's really an example
of using it for good.

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But steganography could also be used

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for covert communication,

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it can be also be used to
conceal malicious code,

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like malvertising, or
phishing, or exploit kits.

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So let me give you a really simple

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steganography illustration.

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Taking this image, image1.jpeg,

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I'm going to add a text
file to that image.

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So the image is the cover,
the text file is the message.

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And then I'm gonna end
up with final1.jpeg.

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Now, does it look exactly
the same as image one?

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Well, absolutely it should

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because I haven't changed
anything in the cover image.

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The picture's exactly the same.

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But now I've embedded the
text file in that picture

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and I wanna show you
absolutely how simple that was.

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Dropping into a command prompt,

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copy/bimage1jpeg=text1.text final1.jpeg,

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which says combined text
one text and image1.jpeg

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to give the output of final1.jpeg.

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And if I opened up final1.jpeg in notepad,

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well, what you would see,

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and the only message I've
actually put in there is my name

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that when they got combined,

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there's my name, right?

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There's the message
embedded in that picture,

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now, if you didn't know to
open that up in notepad, right?

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You'd never have any idea whatsoever

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that there was a message
embedded in that picture.

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So the difference between
steganography and cryptography,

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well one is the purpose, right?

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Steganography the purpose is to conceal.

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We often think of it as covered writing.

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Cryptography our purposes
are confidentiality,

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integrity and non-repudiation.

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There's a difference in
communication channel

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in steganography, the
existence of that secret

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communication channel is not known,

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in cryptography the existence
of the communication channel

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is known.

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And then we have these
mathematical transforms

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or transformations.

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Mathematical transforms or transformations

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are not used steganography

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but they are used in cryptography.

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That was a short little lesson,

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brings us to a three second challenge.

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Oh, everybody's gonna get this one, right?

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This is the practice of concealing data,

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it's what our whole lesson was about.

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1, 2, 3, steganography.

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Number two, hidden data
used to prove ownership.

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I said sometimes there
was good uses, valid uses.

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1, 2, 3, this was a digital watermark.

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Number three, malicious code
embedded in advertising.

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We didn't really talk about this,

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I used this term really, really quickly.

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When malicious code,
malicious code is embedded

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in advertising, what are we gonna call it?

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1, 2, 3, and that's gonna be malvertising.

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Number four, a carrier that
hides a secret message,

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1, 2, 3, that's gonna be the cover image.

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Remember we said it could be text,

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it could be audio, it could be
a picture, it could be video.

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And lastly, number five,

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the study of detecting
messages using steganography.

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1, 2, 3, and that's
gonna steganalysis, okay?

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That brings us to our security and action

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about malvertising.

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Your marketing term,
heard about malvertising

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at a seminar, and now wants to learn more.

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And they've asked you to explain

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what it is and how it works.

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Now, bearing in mind that
they're not very technical

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what would you tell them?

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Now, also, bearing in mind, we didn't talk

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about it very much, and
what would you tell them?

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So go ahead, put me on pause.

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Think about this for a minute

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then come on back and
we'll do our explanation.

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Malvertising is a practice
of placing malicious

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or malware lighting advertisements

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onto a legitimate online
advertising network or a webpage.

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Now, a common technique,
and why we're talking

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about it here in this lesson,

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is the malicious code is
hidden in a cover image,

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a graphic file, or in white space,

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or in an audio file, right?

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And that hiding technique
is known as steganography.

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Now, little to no user
interaction is required

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to become infected, right?

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It can be as simple as
visiting the webpage.

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Now, maybe they downloaded the graphic

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or you know, downloaded a file.

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But a lot of times just by being

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on the page where that graphic is,

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or that text that file is, the
system can become infected.

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And that, my friends, is the relationship

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between malvertizing and steganography

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being able to explain that,
absolutely, security and action.

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It's a pretty small word cloud

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but make sure that you
know all of these terms.

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When you're ready

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we're gonna do a 10
question quiz together.

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I'll see you there.