Let's open up this skill just a little bit different. It was such a beautiful day outside.
I wanted to come outside and enjoy some of it. Now we're going to be talking about deep packet
inspection and there's actually a point to me being outside as well. I'm going to show you
here in just a minute. But when we discuss deep packet inspection we're talking about actually
taking a look inside of the individual packets that go to and from our destinations across the
internet or internal networks. And those packets contain bits of information. Now normally those
packets are encapsulated or encrypted. As a security technician or administrator inside of
an organization, whether it be a large or small organization, we're usually tasked with ways to
be able to prevent things like Netcat from coming into the network on the individual systems. Now
that's a little bit complex to do because sometimes Netcat can be encapsulated or packaged
up inside of something that we don't normally have access to. And that's where things like
deep packet inspection come into play. Because deep packet inspection is the actual inspection
of every single packet that comes through, opened up, and we get to see what's inside. Now I'm going
to show you an example of that in real world here in just a moment. But I also wanted to give you
an example of it in everyday life. Behold my mailbox. And what we usually have whenever we
get mail is we open up and we have a package here. This is not a real mail package. This is just
something I found for my electric fireplace that got installed. And we'll look at it here in a
second. But pretend that this is a packet that came from your individual computer system to a website
that just happens to be my mailbox. Now normally the post office, at least here in the United States,
doesn't open up every piece of mail and inspect it. A little bit of an exception for the DOD folks
out there, especially if you're deployed. However, this package that I got in the mail was sent to me
by somebody else that doesn't live on this site, right? So they went through and boxed it up,
taped it up, put the addressing on it, the to and from and everything, and I got it in my mailbox.
Now the post office doesn't know what's inside of this package. They can shake it and hear that
there's something in there, but they're not going to open it up and actually take a look.
It could be that it's a bunch of dice for my D&D game that's going to happen later today.
Or it could be that it's a bunch of different things that I just found randomly in my junk drawer.
Who knows? But the point is that it goes from the sender to the receiver and is not inspected.
Whereas a deep packet inspection in this sense would be that the sender puts the package in the
mail, the post office gets it, opens it up and sees that it's a bunch of little fake crystal things
that would go in an electric fireplace. And then they put it back together and they send it to
whoever the recipient is, and in this case me and my mailbox. So avoiding deep packet inspection
is kind of critical for us in the pen testing community because a lot of the stuff that we've
built so far throughout our course together relies on the fact that it can evade and get around
different security systems. So what we're trying to do is put a package together and send it from us
to the recipient without anybody taking a look at it. And deep packet inspection has many different
ways of being accomplished and we'll take a look at a couple of those as we go throughout this skill.
But I kind of wanted to point out how deep packet inspection would work on a physical level
because this is how I learned it.