What is a firewall? A firewall is a system that is designed to
prevent unauthorized access from entering a private network by
filtering the information that comes in from the internet. A firewall blocks
unwanted traffic and permits wanted traffic. So a firewall's purpose is to create a safety
barrier between a private network and the public internet. Because out on the internet, there's always
going to be hackers and malicious traffic that may try to penetrate into a private network
to cause harm. And a firewall is the main component on a
network to prevent this. and a firewall is especially important to a large
organization that has a lot of computers and servers in them. Because you don't want all those devices
accessible to everyone on the internet where a hacker can come in and totally disrupt that
organization. That's why you need a firewall to protect
them. A firewall that's used in computer networks
is very similar to how a firewall works in a building structure. In fact..this is where the word 'firewall'
came from. A firewall in a building structure provides a barrier so that in the event of
an actual fire, on either side of a building, the firewall is there to keep the fire contained
and to keep it from spreading over to the other side. So the firewall is there to keep the fire from destroying
the entire building. But if the firewall wasn't here, the fire
would spread to the other side and the whole building would be destroyed. And a network firewall works in a similar
way as a structure firewall. It stops harmful activity before it can spread into the other side
of the firewall and cause harm to a private network. In today's high-tech world, a firewall is
essential to every home and especially a business or an organizaton to keep
their network safe. A firewall works by filtering the incoming
network data and determines by its rules if it is
allowed to enter a network, these rules are also known as an access control list. These rules are customizable and are determined
by the network administrator. The administrator decides not only what can
enter a network but also what can leave a network. These rules either allows or denies permission. So as an example, here we have some rules in a firewall's access control list. It shows a list of IP addresses that
have been allowed or denied by this firewall. And as you can see, traffic from some IP
addresses are allowed to enter this network..but traffic from one IP address has been denied. So, if traffic from this IP address tried to
get into this network, the firewall will deny it because
of the rules that are set in the firewall.. But the other IP
addresses are granted access because the rules Allow them. Firewalls don't just make rules based in
IP addresses, but they can also make rules based on domain names, protocols, programs, ports, and keywords. Let's say in this example, the firewall
rules are controlling access by port numbers. and let's say that the rules have allowed
incoming data that's using port number 80, 25, and 110, and the data using
those ports have been given access to this network. So any incoming data that's using those
ports, can pass through the firewall. But also in this firewall, the rules have
denied any data that's using port numbers 23 and 3389. So any incoming data that's using those
port numbers, the firewall will deny access and it won't get passed the firewall. So in a nutshell this is how firewalls basically
work. Firewalls come in
different types. One
type is called a host-based firewall, and this
is a software firewall. This is the kind of
firewall that is installed on a computer and it
protects that computer only and nothing else. For example, later
versions of Microsoft operating systems come
pre-packaged with a host-baseball firewall. And you can see that example here. There are also 3rd party host-based firewalls
can be purchased and installed on a computer. So for example, Zone Alarm..which is a popular 3rd
party host-based firewall. And also a lot of antivirus programs will
have a built in host-based firewall. Another type of firewall is called a network-based
firewall. A network-based firewall is a combination
of hardware and software, and it operates at
the network layer. It is placed between a private network and the public internet But unlike a host-based firewall, where it
only protects that computer, a network-based firewall protects the entire network, and it
does this through management rules that are applied
to the entire network so that any harmful activity
can be stopped before it reaches the computers. Network-based firewalls can be a stand alone
product ...which is mainly used by large organizations. They can also be built-in as a component of
a router..which is what a lot of smaller organizations rely on. Or they can also be deployed in a service
provider's cloud infrastructure. Now, alot of organizations will use both network-
based and host-based of firewalls.. They will use a network-based firewall to
protect the entire network as a whole...and they will also use host-based firewalls for
their individual protection for their computers and servers. And by doing this, it'll ensure maximum protection . Because if harmful data just so happens to
get passed the network firewall...the host based firewalls on each computer will be there
to stop it. So thank you everyone for watching this video on firewalls. Please subscribe and I'll see you in the next video...thank you.
