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Firewall - What is, Types, Working and Functions

Firewall - What is, Types, Working and Functions

Let’s look further in this blog and review the Firewall, its history, its working of Firewall, Firewall advantages, and disadvantages, and many more exciting insights.

Similar to a security guard, a firewall screens and investigates connections to and from your computer or network in accordance with a predetermined set of rules. While every computer has the most fundamental firewall security.

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What is Firewall?

A firewall plays a crucial role as a protective barrier between a computer network and external networks, such as the Internet, guaranteeing robust network security. It actively utilizes pre-established security rules to diligently monitor and regulate incoming and outgoing network traffic. By examining data packets and applying these rules, a firewall proactively strives to eliminate unauthorized access and effectively neutralize potential threats posed by malicious activities.

What is Firewall?

To accomplish its objectives, a firewall examines the characteristics of data packets, including source and destination IP addresses, ports, protocols, and content. Based on these factors, it determines whether to permit or block the packets. This approach enables firewalls to effectively manage network traffic and provide defense against potential threats, such as unauthorized access attempts, malware infiltration, and other cyber risks.

Firewalls can be deployed in diverse forms, such as hardware appliances, software applications, or a combination. They can be strategically positioned within a network infrastructure, including at the network perimeter, between network segments, or on individual devices. This flexibility allows organizations to establish multiple layers of protection and create secure zones within their network architecture.

Moreover, firewalls offer additional security functionalities beyond access control. For instance, Network Address Translation (NAT) allows multiple devices within a network to share a single public IP address, enhancing privacy and network management. Furthermore, firewalls often support Virtual Private Networks (VPNs), enabling secure remote access to the network, bolstering privacy, and ensuring encrypted communication channels.

Why do You Need a Firewall?

Networks lacking protection are exposed to any traffic attempting to get into your systems. Network traffic, whether harmful or not, should always be monitored.

A wide range of advantageous opportunities become available when connecting personal computers to other IT systems or the internet. Facilitate online and security technology can be sacrificed in exchange for uncomplicated collaboration, sharing of resources, and enhanced creativity. Users run the danger of becoming the victims of malware, online fraud, identity theft, and hacking if they connected their machines to a network or to the internet.

Once a bad actor learns about your network and devices, they can quickly find them, access them, and expose them to ongoing risks. 24/7 internet connectivity increases this risk because your network can be accessed at any time.

The filtering of content is another function of firewalls. For instance, a school can set up a firewall to block individuals from accessing adult content on their network. Similar to this, in certain countries the government maintains a firewall that can bar residents from accessing specific areas of the Internet.

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History of Firewall

The history of firewalls can be traced back to the early days of computer networks and the emergence of the Internet. Here is a summarized history of firewalls along with the corresponding years:

History of Firewall
  • 1987: The initial commercial firewall, referred to as the Raptor Firewall, was developed by Digital Equipment Corporation (DEC). This pioneering firewall served as a fundamental packet-filtering firewall solution.
  • 1992: Marcus J. Ranum was responsible for the creation of the Firewall Toolkit, a comprehensive resource encompassing essential tools and software components required for the construction of firewalls.
  • 1994: Check Point Software Technologies released FireWall-1, a widely used firewall software that introduced stateful inspection.
  • 1995: The Internet Engineering Task Force (IETF) published RFC 1858, the first standard for IP packet filtering firewalls.
  • 1998: The development of Network Address Translation (NAT) technology enabled multiple devices in a private network to share a single public IP address, enhancing firewall capabilities.
  • 1999: Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS) emerged, integrated into firewalls to detect and respond to real-time network attacks.
  • 2000: The IETF released RFC 2979, a new standard defining the requirements for firewalls supporting Network Address Translation.
  • 2004: Next-generation firewalls (NGFW) were introduced, integrating traditional firewall functionality with additional features such as application awareness, user identification, and content filtering.
  • 2010: The rise of cloud computing led to the development of cloud firewalls or virtual firewalls designed to protect virtualized environments and cloud-based applications.
  • 2020: The adoption of Software-Defined Networking (SDN) and Software-Defined Firewalls (SDFW) allowed for more flexible and scalable firewall deployments in virtualized and cloud environments.

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Types of Firewall

Stateful Firewalls

A “stateful” application in computer science is one that stores information from earlier interactions and occurrences. Instead of analyzing every packet, a stateful firewall stores information about open connections and uses this knowledge to evaluate incoming and outgoing traffic.

Stateful firewalls make decisions by heavily relying on context. For instance, if a connection’s outgoing packets require a specific type of response, the firewall will only permit incoming packets on that connection provided they also include the desired response.

Firewall-as-a-service (FWaaS)

The more recent paradigm for providing firewall capabilities through the cloud is firewall-as-a-service (FWaaS). Another name for this service is “cloud firewall.”

 Similar to how conventional firewalls enclose an organization’s internal network, FWaaS creates a virtual wall around cloud platforms, infrastructure, and applications. FWaaS is frequently more effective than traditional firewalls at securing cloud and multi-cloud assets.

Web application firewalls (WAF)

WAFs, assist protect online applications from dangerous users, whereas conventional firewalls protect private networks from harmful web apps. By filtering and observing HTTP traffic between a web application and the Internet, a WAF aids in the protection of web applications.

It typically guards against attacks like cross-site scripting (XSS), file inclusion, SQL injection, and cross-site forgery, among others.  

Next-generation firewalls (NGFW)

NGFWs are firewalls that combine traditional firewall functionality with a number of extra features to combat threats at various OSI model layers.

NGFWs examine packets significantly more thoroughly than conventional firewalls do. Deep inspection can examine packet payloads and the applications that the packets are accessing, among other things. This enables the firewall to implement filtering rules with greater specificity.

Proxy-based firewalls

These intermediaries* between clients and servers are proxies. Clients connect to the firewall, which inspects the outgoing packets before establishing a connection with the target (the web server).

The firewall will also intercept a request from the web server trying to send a response to the client, inspect the packets, and then relay the response through a different connection to the client. Effectively preventing a direct connection between the client and server is a proxy-based firewall.

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Working of Firewall

The operation of a firewall centers around its capacity to oversee and manage network traffic based on predefined security rules. Functioning as a safeguarding barrier between a computer network and external networks, such as the Internet, a firewall scrutinizes all incoming and outgoing network traffic, including data packets, determining whether they should be permitted or obstructed.

Firewalls employ security rules that delineate permissible network traffic. These rules typically rely on factors like source and destination IP addresses, port numbers, protocols, and specific content within the data packets. As data packets traverse the firewall, they undergo scrutiny in accordance with these defined rules. The firewall assesses the characteristics of each packet, comparing them against its rule set to determine whether they should be granted passage or blocked.

Working of Firewall

By enforcing access control policies, firewalls make determinations regarding the allowance or denial of network traffic based on the outcomes of packet inspection. Authorized traffic that conforms to the rules is granted permission, while unauthorized or potentially harmful traffic is impeded.

Firewalls frequently incorporate Network Address Translation (NAT) functionality, enabling multiple devices within a network to share a single public IP address. This NAT feature provides an additional layer of security by concealing the internal network structure.

Logging and auditing play crucial roles in firewall operations. Firewalls maintain logs of the network traffic they process, capturing details such as source and destination IP addresses, ports, protocols, and the actions taken by the firewall (allow or block). These logs are invaluable for troubleshooting, monitoring network activity, and identifying potential security incidents.

Modern firewalls may integrate advanced security features to fortify protection. These features can encompass intrusion detection and prevention systems (IDS/IPS), deep packet inspection (DPI), Virtual Private Network (VPN) support, anti-malware scanning, and application-specific controls.

Firewalls necessitate continuous monitoring and updates to remain effective against emerging threats. This entails keeping the firewall’s software and security rule sets up-to-date and addressing new vulnerabilities and attack patterns.

Functions of Firewall

Here are some key functions of a firewall:

  • VPN Support: Firewalls often provide Virtual Private Network (VPN) support, allowing secure remote access to private networks over the public Internet. They can authenticate and encrypt VPN connections, ensuring that sensitive data transmitted between remote users and the network remains secure.
  • Logging and Auditing: Firewalls generate logs that record information about network traffic, such as source and destination IP addresses, ports, and timestamps. These logs can be used for troubleshooting, forensic analysis, compliance audits, or monitoring network security events.
  • Content Filtering: Some firewalls include content filtering capabilities to control and restrict access to specific types of websites, applications, or content categories. This feature helps organizations enforce acceptable use policies and protect against potential threats or inappropriate content.
  • Bandwidth Management: Firewalls can be configured to manage and allocate network bandwidth resources. They can prioritize certain types of traffic, such as voice or video, over others to ensure optimal performance and prevent network congestion.
  • Denial of Service (DoS) Protection: Firewalls can help mitigate Denial of Service attacks by detecting and blocking excessive or malicious traffic that aims to overwhelm network resources. They can employ various techniques, such as rate limiting, traffic shaping, or packet filtering, to mitigate the impact of such attacks.

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Main Advantages of Firewall

  • Computers are protected from viruses, malware, and other destructive codes by firewalls. Additionally, if the computer is protected by a firewall, the user can carry out their office tasks in a secure manner.
  • Given that the majority of threats occur through virtual traffic, it is one of the most important benefits of firewalls. Consequently, if you have firewalls installed on your device. If so, it will continue to run in the background and examine all communications.
  • Even if you lack technological expertise, you may still install firewalls on your computer. Additionally, no expert assistance is required for deploying the firewalls.
  • While online, a user expects total privacy, yet certain unforeseen circumstances may make them uncomfortable with this expectation. As a result, if they employ firewalls in that situation, it will ensure that their high level of privacy is maintained.
  • Some hackers get unauthorized access to users’ computers in order to engage in unlawful activity. They continue seeking for devices to break into in order to get private information like credit card numbers.

Limitations of Firewall

  • For their customers, firewalls also have a number of drawbacks, with cost being one of them. For businesses, purchasing firewalls can be expensive because they need payment.
  • Several websites with viruses or malware are blocked by the firewall. Although this item may benefit its users, it frequently causes issues for huge businesses.
  • The security tools that remain active in the background of the computer are firewalls. Additionally, the computer’s performance will be poor because there are several tabs open and the firewall is on.
  • You should install the anti-virus software if your machine already has a firewall installed. In order to execute the malware detection test and get rid of all these viruses and malware.
  • Despite the fact that nowadays small businesses feel comfortable purchasing firewalls for their computer hardware. However, many large firms require a specialized staff of IT professionals who can handle all firewall maintenance tasks.

How to Use Firewall Protection?

Make sure your firewall is configured and maintained properly to keep your network and devices secure. Here are some pointers to help you strengthen the security of your firewall:

  • Update your firewalls frequently as soon as you can: Your firewall is updated against any recently disclosed weaknesses courtesy of firmware patches.
  • Use antivirus protection: To protect your system from viruses and other infections, you need also use antivirus software in addition to firewalls.
  • Limit the host and ports that are open; restrict all incoming and outgoing connections to a narrow whitelist of reliable IP addresses.


In this blog, You now know what a firewall is and how it functions as a result of this course. Additionally, you learned about the many kinds of firewalls and how to operate them. Furthermore, we tried to explain the history and the difference between firewall and antivirus. In the modern era, cybersecurity is a booming industry. If you want to learn ethical hacking to defend networks and devices from hackers then you are in the right place.

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About the Author

Technical Lead - AWS Solutions Architect

Shivanshu is a Technical Lead and AWS Solutions Architect passionate about utilizing Cloud technology to empower businesses. Proficient in AWS, Terraform, and GCP, he crafts innovative solutions to propel companies forward. As an enthusiastic writer, he shares his expertise to inspire others in this field.