- [Instructor] Denial-of-service attacks
have been around for quite some time.
Now, what I want to do here
is actually provide you with an overview
of the different denial-of-service
and distributed denial-of-service attacks,
and the difference between them, right?
And basically, denial-of-service attacks
can be divided into three different categories.
Direct, reflected, and amplification attacks.
And basically, a direct attack
is whenever the source of the attack generates packets,
regardless of the protocol,
regardless of the application and so on.
And they're actually sent directly to the victim,
just as the word says.
Now, in a reflected attack,
things are a little bit different.
And this is because
with reflected denial-of-service attacks,
attackers send to sources spoof packets
that basically appear to be from the victim
and then those sources become unwilling participant
in the actual attack themself.
And of course, send their response traffic
back to the unintended victim.
Now, in most cases, this is actually done
using things like UDP as the transport mechanism
because it's actually really easy to be spoof
due to the lack of the three way handshake.
For example, if the attacker actually decides
he want to attack a victim,
he can actually send packets like
NTP packets, DNS packets, and many others
that actually use UDP for communication.
Now, let's cover the last type of denial-of-service attack
and that's actually an amplification attack.
And basically, an amplification attack is a form
of reflected denial-of-service attacks
in which the response traffic,
that is actually sent by the unwilling participant,
is actually made up of packets that are much larger
than those that were initially sent by the attacker.
Now, an example of this attack
is an attacker actually sending DNS queries to a DNS server
that is actually configure as an open resolver.
And then the DNS server, or the open resolver,
will reply with responses
that are much larger in packet size
than the initially query packets.
As you actually can see in the screen.