What exactly is a firewall? how does a firewall work? - 5 basic firewall types (2021)

of any particular traffic which is coming in so it is keeping a track of previous packets which has gone in and the new packet which is coming in hello friends welcome to itk fun day your own channel where we make it interesting for everyone and in this video we will understand about firewall there's a famous saying where there is a will there is a way but if you ask me i often say that where there is a will there is a wall and you need to break that wall to find your way and that wall

in networking is none other than a firewall so if someone wants to get into your network he or she needs to break this firewall at first place so in this video we'll understand what is a firewall with a basic real-life example we'll understand the basic architecture of how firewall works and at the end we'll also understand about some basic types of firewall which we use so without further ado let's get started thank you friends if you're new to itk funday channel we make it interesting for everyone be it i.t or non-iit we discuss all the

latest tools and technologies products productivity hacks and career tips on this channel so if you are new and if you like the content do consider subscribing thank you so friends if you take a real life example you can take an example of a housing society where we have three different buildings and people staying in their own apartments within this society and then there is this security entrance where the security guard is making sure that only the legitimate and the valid users or guests are only entering the society how he decides it he decides it on

the set of security guidelines which the society has given it to him this red guy protecting the gate is our firewall the security guard ensures that only the legitimate and the valid uh you know users or guests or visitors enters the society so firewall is nothing but a security guard firewall is a security conscious router as well you can say uh which enables you know that only the legitimate network traffic gets into uh the you know the network so friends uh let's quickly discuss about the two main categories under which a firewall uh can be

divided so those two categories are software firewall and hardware firewall so hardware firewalls are actually the hardware appliances which you put in the perimeter in your network boundaries so that no intrusion can happen and that particular hardware firewall can be equated with the security gate and the security personnel who's you know who's securing your whole society but a software firewall is also uh you know an operating system level firewall which is installed in on your specific systems like you see windows firewall is a very good example now the question arises whether we need a hardware

firewall or a software firewall so answer is you should ideally be using both why it's very natural because suppose this security guard is a very good guard and the gate is very you know very strong gate still if you are staying somewhere here you still would put a lock in your house to give that additional level of security to your house because the intrusion might not be external it could also be internal and your firewall guy is sitting only securing the outside traffic coming into the you know the your network but what about if some

intrusion happens from here to here then what would happen if something happens within the society so your software firewall acts as a second layer of protection so always understand this difference between the two also your hardware firewall can be a standalone appliance which you know which can be deployed only looking and making sure that you know it is acting as a dedicated firewall or else most of the routers are also now coming up with the firewall functionality so you can have both a router and a firewall so a router's responsibility is to route the traffic

to the you know correct direction wherein the firewall would ensure that that only the legitimate traffic is passing through that router so a small great company or a small usage uh scenario might take both into one uh device a router plus firewall but maybe in at an enterprise level you might have a dedicated firewall device and a dedicated router so it depends so yes so this is the basic understanding of firewall and the two broader categories now we'll dig deep into the basic architecture of how firewall is designed so friends this is a high level

architecture of a firewall design uh so as you can see from on the left the traffic is coming from your internet service provider this is your extranet your external network and then uh you know these are the two firewalls which we have placed this is the external firewall and this is the internal firewall you you know you can design your architecture with a single firewall also but this is to just give you that additional layer of security and also the benefit of this is that if you have an external firewall and an internal firewall in

between you could have your parameter network in which you can uh host your dmz which is demilitarized zone now what is a demilitarized zone this is an area which is lesser restricted than your actual local area network in this area you can host the servers or the applications which needs lesser restrictions like your mail server anyone on the internet might want to connect to your mail server anyone in the internet might want to connect to your web server with lesser restrictions so instead of placing it within your local area network you place it into dmz

so dmz is also a functionality which is uh you know designed using a firewall parameter perimeter network so this is your external firewall this is your internal firewall the you know any request which comes goes through uh the rules which have been set up and based on that uh the decision is made whether this should go ahead or they should go into trash and then you have specific software uh firewalls which are deployed in every machine at an operating system level so yeah this is a you know an overall architecture of a firewall and then

uh always understand that there is a priority in which uh you know the rules are set so anything which is going from left to right in this diagram so what is in your left left is external and right is uh internal okay so from left to right you have lower priority what does that mean that these would be more restricted anything coming from outside to inside your network would be more regressively uh tested okay where in anything coming from you know this right side of your local area network towards outer network would be you know

lesser restricted because this has a higher priority so take for example if we take our society a visitor entering into the society would be grilled more by the security guard whereas an owner if he is walking past the security entrance gate for a morning walk maybe outside uh the society premises then the security guard won't ask that many questions or maybe none no no questions would be asked from that particular owner right because he has the higher authority so in the similar way when you design your firewall rules these are designed in in this manner

now what we will understand we will understand uh some basic broader categories and types of firewalls which we have the category you know these are ever expanding and we have new technologies coming up but these are some basic types of firewalls which you should be aware of so friends now let's understand the five basic types of firewalls which we use in networking so the most basic type of firewall is packet filtering firewall it is the most basic but one of the most widely used and efficient firewall type uh it inspects any particular network traffic at

a very specific packet level so it would check the source and the destination ip addresses and the port information and based on that it would decide and based on the rules which are given to that particular firewall it will decide whether this packet is a legitimate packet or not so what are the good things about packet filtering the packet filtering firewall is very inexpensive it's very cheap secondly it is very efficient because it is only inspecting at a packet level uh but the downside is that it is not that secure uh you can have some

attacks like ip spoofing now what is ip spoofing ip spoofing is if someone injects a wrong ip within that particular packet or forged the ip address and you know it can trick this particular firewall using ip spoofing kind of methods that's why packet filtering is not considered as the most secure but still it is very widely used because it's very effective uh so uh packet filtering uh if we correlated with our society example it's as if you know any visitor is coming to the gate and only telling that he wants to visit a particular house

this is the flat number this is the owner name and he wants to meet and the security guard only checks that okay yes this is the flat number and here this particular owner stays and he just lets this particular visitor go in but what if this particular visitor is forging uh you know this identity of his and there is no inspection happening overall so this particular visitor could go and do some malicious activity as well because there is no further validation or the contextual value relation happening uh you know at this kind of packet filtering

firewall so coming to the second type is the stateful inspection now stateful inspection is an intelligent version of packet filtering where the firewall is also understanding the overall context of any particular traffic which is coming in so it is keeping a track of previous packets which has gone in and the new packet which is coming in so uh it it would give the additional layer of security because it's not just blindly taking one packet at one time and allowing it so take for example if any visitor is coming into the society uh that guard is

not just randomly letting this particular visitor go in it is validating maybe you know calling the owner checking whether you know this particular visitor was called for uh you might understand what is your uh objective of coming in take more details something like that so adding more context would give more security adding more context to it uh gives you a stateful inspection so this packet filtering is stateless you're not consider worried about the state you're taking one packet at a time and you're taking a call here in whereas in stateful you are understanding the context

so it is a slightly higher you know secured version but obviously it comes with a cost it would be slightly expensive it would be slightly slower but yeah it all boils down to your requirements the third one is circuit level gateway now in circuit level gateway uh the firewall establishes uh you know a circuit a tunnel of sorts between source and the destination it connects both the network at once and then it just goes out the firewall says i have now connected you i have validated i have connected you through this particular port now do

whatever communication you want to do the firewall won't interfere in that so vpn is kind of you can understand a similar concept where you create a vpn tunnel and then you continue to interact so suppose if you are doing a telnet from your client machine to a server and if there is a circuit level gateway in there so the moment you connect to your telnet port that particular telnet channel would be created and then the firewall would just you know won't interfere in the further communication now again again it has some goods and the bad

so good is once it is there uh the channel is created it's very seamless but again what happens if you know if something goes wrong because now the firewall is not at all taking care of this circuit it might happen that some kind of interference might happen in this so again this has uh some drawbacks now application proxy gateway this is the by far the most superior version it combines all the goods of the top three and then offers something more so now application proxy gateway works at a you know higher level of osi model

so it it works at an application layer and what it does is it takes the application context into picture and then deploys the firewall rule so the firewall is very far intelligent compared to this because these are basically working at a network layer or a transport layer this particular proxy gateway is dedicatedly working at an application layer so it it knows what this particular application is expecting so suppose there is a web application which is expecting some sort of an http traffic to come in now this particular firewall could be deployed with an intelligence to

assess the packets which are coming are actually in the desired format or not and it might see that okay this particular http format which is coming is not correct it might redesign it to the in a manner in which the application is requesting also suppose there is certain pages of this web application which are static so those can be cached at a this particular gateway level so the request might not again go back and come for these kind of static pages it this particular firewall gateway could uh manage this on its own so this is

by far the more most intelligent version of all the four which we have talked about but very expensive and takes a lot of maintenance and designing these kind of firewalls are way more complex technically and last but definitely not the least is firewall as a service now what is firewall as a service you you might know that now more and more applications are going on to the cloud and you have these big cloud providers uh who are offering you firewall as a service so you take for example if we talk about google cloud platform so

in google cloud platform you can design your whole firewall just from the web portal or the gui of cloud vendors and you don't have to worry about the internal functioning of it you just need to decide okay what kind of rules you want you just go there and you just select whatever rules inbound rules or outbound rules you want and rest all will be taken care under the hood by the cloud provider so this is now very very much emerging which is called as firewall as a service so friends this brings us to the end

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