What Does a Firewall Do? An Overview on Firewalls



What Does A Firewall Do?


A firewall is a cybersecurity solution that safeguards your network by monitoring, filtering, and restricting traffic entering and exiting it. In a nutshell, a firewall acts as a barrier to ensure that only good traffic enters and bad (malicious) traffic does not. It accomplishes this by distinguishing between trusted and untrusted traffic and taking appropriate action. (Fortigate Firewall)


Consider a firewall as a sentry responsible for raising and lowering a castle drawbridge. It is their responsibility to check and oversee all traffic entering and exiting the castle. If they notice someone strange or unauthorised attempting to enter or leave the castle, they can either let or prevent the suspected individual (or people) from doing so. Firewalls are similar to routers, but they protect data rather than people.


One or more levels of your cybersecurity protection include firewalls. They assist in the defence of your network against a variety of threats, including malware and brute force attacks.


A firewall secures the devices that are linked to your network by preventing illegal access from the internet. This might include your laptops, servers, and linked gadgets like wireless printers and smart thermostats for businesses. Indeed, a useful and required tool!


Hardware and software firewalls are two types of firewalls.


Hardware and software firewalls are two types of firewalls to be aware of. A hardware firewall, as the name implies, is a physical device that filters network traffic in the same way that a traffic router does. Its function is to secure networks and endpoints. Hardware firewalls, on the other hand, seek to safeguard your entire network with only one device. As a result, they are vulnerable to attacks on the network’s interrelated relationships.


A more granular option would be to use software firewalls, which would entail installing a firewall on current individual local devices. A software firewall, which is typically found in antivirus software and operating systems, works in the same way as a hardware firewall. It inspects and filters traffic for that particular endpoint device only.


Is there a benefit to using one over the other? Using both hardware and software firewalls to establish levels of security is a common strategy for large networks.


Other Firewall Types That Answer the Question “What Does a Firewall Do?”


Firewalls, as previously said, exist in a variety of shapes and sizes and are utilised in a variety of applications. You can classify them based on their format, deployment location, or what they protect. As a result, learning the many varieties might be challenging.


It’s easiest to understand what a firewall performs if you divide down the different types by processing modes. Processing modes refers to the classification of firewalls based on their operating purpose. This can help you envision what a firewall accomplishes, as well as how and why it works the way it does.


Firewalls with packet filters


This is the kind of firewall we talked about earlier in this post. A packet-filter firewall employs rules to decide whether or not data packets are allowed to enter your network. The firewall rules are access controls that inform the firewall what data packets to search for. Data packets contain the following sorts of information:



The stateless firewall (yep, we’re now discussing “types of sorts of firewalls”… it’s firewall conception!) is a packet-filtering firewall that uses these specific “access controls.” In a very basic sense, the stateless firewall checks incoming and outgoing traffic against the set of rules/access controls that it has been given. It’s essentially a network perimeter firewall, which means it doesn’t monitor traffic inside the network. Because it relies on a pre-determined (static) list of rules, this is also known as static packet filtering.


A simplified diagram of a stateless packet filter firewall in action. The first example illustrates the firewall allowing approved (trusted) traffic through. The firewall in the second example is preventing unauthorised (untrusted) communication.


There is, however, a more dynamic sort of packet filtering firewall. This is known as a stateful firewall, and it employs dynamic packet filtering. It works similarly to a stateless firewall in that it uses preset rules to filter incoming and outgoing traffic. However, once traffic enters the network, the firewall goes above and beyond its counterpart by monitoring active sessions. A stateful firewall, in particular, monitors the traffic’s source, ports, and destination IP addresses. Any responses attempting to exit the network must match the data that was entered, otherwise the firewall will stop them.


Firewall Proxy


This firewall serves as a bridge between two systems that want to communicate through a client. This link between internal and external systems acts as a buffer. Incoming traffic is intercepted by the proxy firewall, which then functions as a substitute. Endpoints are protected from potential attacks by this layer of defence.


A proxy firewall is also referred to as a gateway firewall or an application-layer firewall. The fact that they filter traffic at the OSI application layer gives them their names. Because of its thoroughness, this firewall provides a better level of security, but the tradeoff is that the extra effort can slow down performance.


Firewalls for circuit-level gateways


The circuit-level gateway firewall’s job is to authenticate TCP (Transmission Control Protocol) handshakes of traffic attempting to enter the network at the OSI (Open Systems Interconnection) session layer. This is done to ensure that the connections are safe. These firewalls are usually integrated into existing software and do not inspect data packets. This results in a transaction that is low-maintenance and efficient. It is, however, a firewall that is more vulnerable to some sorts of cyber attacks due to the lack of content screening.


Firewalls for the MAC Layer


Incoming traffic is vetted by the MAC (Media Access Control) layer firewall in a unique way. This firewall detects the MAC addresses of the host computers attempting to access it by functioning in the OSI media access control layer. The MAC layer firewall can more readily identify and prohibit undesirable traffic thanks to an access control list connected to MAC addresses.


More Firewalls to Be Aware Of


You’d be mistaken if you thought that was a complete list of firewalls. There are various more sorts of firewalls to be aware of. We won’t go into detail about each of them right now, but we will touch on a few of them briefly to acquaint you with them.


Hybrid Firewalls – As the name implies, this firewall is a combination of many of the firewalls discussed previously. A hybrid, for example, could combine proxy services and packet filtering to act as a more comprehensive device.

DNS Firewall – Another place where traffic flows often and could benefit from the filtering capacity and capabilities of a firewall is the DNS. Because they operate in an external environment, these firewalls are unique.

Web Application Firewalls (WAF) – These firewalls are frequently used to protect websites. They assist in the filtering and control of traffic over HTTP and HTTPS connections.

Next-Generation Firewalls (NGFWs) – These firewalls can be utilised in a variety of ways and offer a little bit of everything. Next-generation firewalls are distinct in that they examine the complete data transaction (i.e., the payload of the packet).


Firewalls Have Drawbacks


Technology isn’t perfect, as we all know. Yes, there are some disadvantages to employing certain kinds of firewalls. Simply compare the benefits and drawbacks of different types of firewalls to determine which one(s) would best serve your organization’s needs. We’ve previously discussed a few. To recap:



Final Thoughts on What a Firewall Does


Although firewalls are just one of many crucial levels of an organization’s effective security defences, they are an essential component that should never be disregarded. While many operating systems and antivirus solutions have firewalls, they frequently fail to satisfy the demands of organisations. This is why businesses should assess their alternatives and seek more complete firewall solutions that provide additional security.


So, the most significant aspect of the answer to the question “what does a firewall do?” is that it keeps harmful and malicious traffic out of your network while allowing valid and trustworthy traffic in.


We hope that this overview helped you better understand how firewalls safeguard your business and the various varieties available. Keep an eye out for future firewall posts as we offer more information about these useful tools!


Now you have the ideas about what does a firewall works, and the type of firewalls. You may continue to explore more interesting articles at The Post City and don’t forget to share this article with your friends / colleagues who might interested in this topic. Thanks for reading !


Learn more: Fortigate Firewall 

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