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OK, so now let's talk about Farmville, you all have heard a word firewall, we know whenever you go



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to buy a new PC and the person who's going to sell you the piece, you say that do not forget to install



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the firewall on your network or if you are working in a company, sometimes a website or the application



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says you are being blocked by a firewall.



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You cannot access this website, go back and go back to the safe mode.



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So what exactly is a firewall?



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Yeah, let's answer this in this lecture.



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So basically firewalls are your networks, the security guards.



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And to be real, they're probably the most important things to implement on your network.



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That's because today's networks are almost always connected 24 by seven to the Internet, a situation



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that makes security very crucial.



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The firewall protects your land resources from invaders that use Internet for unprotected networks while



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simultaneously preventing all or some of your land's computers.



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Now you can use firewalls to filter packets based on the rules that you or a network administrator create



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and configure strictly to eliminate the type of packets which are not intended for your PC.



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For example, let's say you configure your firewall to discard all the packets having the protocol HTP,



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which is hypertext transfer protocol and it is not a secure protocol.



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OK, wait, don't get confused between NHTSA, we are going to see all these protocols in upcoming lectures



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for time being, just understand that HTP and ATP's are two different protocols, that extra DPS is



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more secure protocol.



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So now if you employ a signature or if you imply a rule that says that, please discard all the packets



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that have HTP, your firewall will not allow a packet entering from the Internet having htp a protocol.



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So far, all can operate on multiple layers of the user model and some firewalls can operate up to the



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application layer, which have a great functionality on your PC.



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A firewall can either be a standalone black box or a software implementation placed on a certain router,



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either via the firewall will have at least two network connections, one to the Internet.



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That is the public side from where all the data comes to a network.



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And the other one is the network known as the private side.



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Now, sometimes that is a second wire fall as I'm sorry, there is a second firewall, as you can see



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on the screen now, this firewall is used to connect to servers and equipment that can be considered



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both public and private, like Web email servers.



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I'll show you.



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Just give me a second and.



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Yeah, so you can see this part here.



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This is one firewall.



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This is the first firewall.



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This is the first of all, this is the second firewall in between.



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There are these servers that need to be protected.



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Now, these servers are directly accessible to the normal person, but there is a firewall in between.



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And these servers are also a private property of a company.



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So the zone between two different firewalls, OK, this zone, this zone is known as demilitarized zone.



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That is the.



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And the that is demilitarised zone firewalls are the first line of defense for an Internet connected



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network without any place a firewall, any network that is connected to the Internet is essentially



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wide open to anyone with the technical savvy who seeks to exploit all the resources.



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So, for example, if you don't have this firewall in place, an attacker here, an attacker here can



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directly access your servers.



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And if he's able to exploit one of these servers, he can directly have access to the whole Internet.



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And in this way, your whole Internet can get compromised.



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And that is why firewalls are really very important.



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In the next lecture, we'll have a look at the detection systems, intrusion detection systems and prevention



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systems as well.



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So they are also kind of firewalls which protect your network, but they function.



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There are a couple of differences between firewall and the detection and prevention systems that does



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exclude them in the next lecture.