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What is a Firewall and its Various Types

Since the number of cybercrimes continues to rise, it is more important than ever for people and businesses to take precautions to protect their data. There are, however, several obstacles to enacting the same. You can protect your network and device from potential intruders with the aid of a firewall. This guide will teach you all you need to know about firewalls and how they defend your network from outside threats.

What is Firewall?

A firewall is a security device for a network that monitors and controls the flow of data into and out of the network based on predetermined rules. A firewall is a barrier that separates a private network from the wider Internet.

Like a fence around your home, a firewall prevents unwanted visitors from accessing your computer network. Firewalls are a type of network security mechanism that blocks out intruders. It is a device, either hardware or software, that screens data entering and leaving a private network for malicious activity and blocks it. 

Firewalls can be found in both business and home networks. They play a crucial role in keeping networks safe. A rudimentary firewall is included in most OSes. However, a separate firewall program offers superior security.

Why Do We Need Firewalls?

A firewall is an integral component of any security architecture since it eliminates the need for manual configuration of host-level security measures. Next-generation firewalls have an integrated intrusion prevention system (IPS) that allows them to swiftly and smoothly detect and respond to external threats throughout the whole network, preventing malware and application-layer attacks. They may implement policies to better protect your network and conduct rapid assessments to find and stop harmful or suspicious activities, such as malware.

Why are They so Important?

Next-generation firewalls, in particular, are designed to prevent malware and application-layer assaults. Along with an integrated intrusion prevention system (IPS), these Next Generation Firewalls can swiftly and reliably respond to threats throughout the whole network. Firewalls can perform rapid assessments to identify intrusive or suspect activities, such as malware, and shut them down based on predefined regulations. By deploying a firewall as part of your security architecture, you can control what data may enter and leave your system based on predetermined rules.

Types of Firewall

1. Packet filtering firewall

Firewalls that use packet filtering function inline at nodes where other networking devices, including routers and switches, perform their functions. Instead of simply forwarding data, this form of firewall analyses the protocol headers of incoming packets to determine whether or not they match the authorized IP addresses, packet type, port number, and other criteria. When a packet is identified as malicious, it is usually deleted without further consideration, meaning it is never transmitted and hence never received.

While packet filtering’s security may fall short in some scenarios, it’s worth considering as a low-cost firewall alternative in others. Packet filtering offers a low-cost yet effective defense against common online dangers for businesses with limited resources. Packet filtering may also be used as a layer of defense in larger organizations to monitor department communications and block malicious data.

2. Circuit-level gateway

Circuit-level gateways across the network keep an eye on TCP handshakes and other network protocol session initiation messages between local and remote hosts to ascertain whether the session is legitimate and whether the remote system is reliable. However, they don’t look inside the packages themselves. While packet filtering’s security may fall short in some scenarios, it’s worth considering as a low-cost firewall alternative in others. Packet filtering offers a low-cost yet effective defense against common online dangers for businesses with limited resources. Packet filtering may also be used as a layer of defense in larger organizations to monitor department communications and block malicious data.

3. Application-level gateway

Technically a proxy, but sometimes known as a proxy firewall, this gadget acts as both the network’s gateway and exit. In addition to the service for which the packet was destined (as indicated by the destination port), application-level gateways also filter packets based on additional criteria, such as the HTTP request string.

Gateways that filter at the application layer greatly enhance data security, but they can significantly impact network speed and are only sometimes simple to manage.

Enterprise resources are best shielded from web application risks by application-layer firewalls. In addition to preventing data leaks from inside the firewall, they can also restrict access to malicious websites. However, they may cause a lag in messages sent and received.

4. Stateful inspection firewall

Sensitive hardware verifies whether or not a given packet is part of an active TCP or other network session and does this check for each packet. More security is provided at the expense of network performance than with only packet filtering or circuit monitoring.

Another flavor of stateful inspection is the multilayer inspection firewall, which looks at how transactions progress across various protocol layers of the OSI model’s seven-layer architecture. A stateful inspection firewall is useful for most businesses. These gadgets provide a more comprehensive connection between computers and other assets inside the company firewall and the internet at large. They can also provide excellent protection for network nodes against specific threats like denial of service.

5. Next-generation firewall

Deep packet inspection (DPI), intrusion detection/prevention systems (IDS/IPS), malware filtering, and antivirus software are all typical components of a Next-Generation Firewall (NGFW).

DPI examines the data contained within a packet, as opposed to the protocol header as is done in classical firewalls. A DPI firewall monitors the flow of data throughout a web browsing session, allowing it to determine whether or not the data included in a packet payload, when combined with data from other packets to make an HTTP server response, is valid HTML.

Firewall delivery methods

As new types of IT consumption emerged, so did new ways to set up security. Today’s firewalls might be either hardware appliances, software applications, or cloud-hosted services.

1. Hardware-based firewalls

A hardware firewall is a piece of hardware that provides a safe connection between internal network nodes and external ones. Hardware-based firewalls are independent appliances that don’t drain the host computer’s resources.

These appliances, which can also be known as network-based firewalls, are great for protecting a large number of endpoints in a medium- to large-sized business. It takes more expertise to set up and run a hardware firewall than a host-based one.

2. Software-based firewalls

Host firewall software is deployed on a server or other host device. Each computer or other device requiring security should have host firewall software installed. Hence, software-based firewalls use some of the host device’s CPU and Memory.

Personal computers and other electronic devices can benefit greatly from the security provided by software firewalls, which can block harmful programs and websites. They are able to differentiate between applications on the host and filter incoming and outgoing data accordingly. This allows for granular control since communication to/from one application can be allowed while blocked for another.

3. Cloud/hosted firewalls

Cloud-based firewalls are available from managed security service providers (MSSPs). This hosted service may be set up to monitor either an organization’s internal network or external, on-demand systems. Cloud-based firewalls, also known as firewalls as a service, are an excellent solution for big or widely dispersed companies with security resource gaps since an MSSP may control them. Companies with fewer resources, like as personnel or knowledge, may also benefit from cloud-based firewalls.


In conclusion, a firewall is a crucial component of network security that acts as a barrier between a trusted internal network and untrusted external networks, such as the Internet. Its primary function is to monitor and control incoming and outgoing network traffic based on a set of predefined rules, thereby preventing unauthorized access, data breaches, and cyber threats.


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David Scott
David Scott
Digital Marketing Specialist .


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