Instructor: Now, before we start talking
about network hacking,
you need to have a basic understanding
on how networks work.
Now, we all know that a network usually contains
a number of clients connected to each other,
and clients usually connect to a network
in order to share data or share a resource.
A really good example of a resource
that we all have connected to networks
in order to access is the internet.
So, we connect to Wi-Fi networks and even wired networks
all the time just to access the internet.
Now, all networks, whether it's Wi-Fi or wired,
work on the same principle.
They have a device that is considered as server.
Now, in many cases, for example, in your home network,
this server is your router.
This is also referred to as an access point.
Now, this router or server or access point
is the only device that has access to the resource.
So, none of these clients have direct access
to the resource, even after connecting to the network.
The only way they can access the resource
is through the access point.
So, let's say, for example, you're client number one
and you connected to your home network
over Wi-Fi or over ethernet, over a cable
and then you opened your browser and you typed google.com.
What happens is your computer will send the request
to the access point asking for google.com.
The access point has access to the resource,
which is the internet in this example,
so it's gonna go and look for google.com.
It will receive google.com,
and it'll forward that response to your computer,
and as a result you will see the website
loading on your browser.
So if you actually go to your router at home
and look at it, you'll see at the back
it's connected through a cable to the wall
and this is how it's getting its internet access.
Therefore, it is the only device in your network
that has direct access to the resource
and none of your computers,
none of the computers connected to the network
can access the resource or can access the internet
without the router, without the access point.
So the only way for all of the connected clients
to access the resource is to go through the router.
Now, the data is transferred between clients
and the access point as packets.
So you can think of all of these arrows
as a series of packets being transmitted
between the client and the router as requests and responses.
Now, in Wi-Fi networks,
these packets are transmitted in the air.
Therefore, if you have a wireless card
and you're within range, you'll be able to capture
all of these requests and responses.
So, basically, you'll be able to see
anything that any computer
connected to the same network as you,
thus on the internet,
because they will have to send all of these data
to the access point,
and because they're sending this data in the air
because you're in a WiFi network,
you'll basically be able to capture
these requests and responses.
And you'll be able to see the URLs they visit,
the usernames, the passwords they enter, the chat messages.
Anything they do on the internet will be sent as packets
and therefore you'll be able to capture it and analyze it.
We'll talk more about that
and more about how networks work
as we go through the course
but this is enough to get you going
through the next few lectures, so that you can sniff data,
analyze it and start launching
some cool pre-connection attacks.