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What is a Firewall? Types of Firewall

  • Yashoda Gandhi
  • Jun 21, 2022
What is a Firewall? Types of Firewall title banner

Individuals and businesses must secure their information as the number of cybercrimes grows by the day. However, there are numerous obstacles to its implementation. A firewall is one type of security device that can help you protect your network and devices from intruders. 


In this 'what is a firewall' tutorial, you will learn everything you need to know about a firewall and how it acts as a shield to protect your network.



What is a Firewall?


Firewalls are cybersecurity tools that monitor incoming and outgoing network traffic and allow or prohibit data packets based on a set of cybersecurity rules. They are typically used to protect network nodes from egress and influx of data traffic, as well as specific applications. 


Firewalls protect networks from external attacks by utilizing software, hardware, or cloud-based methods. A firewall's primary goal is to block malicious traffic and data packets while allowing legitimate traffic to pass through. 


To prevent attacks, firewalls examine inbound traffic based on predefined security rules and filter traffic from unsecured or suspicious sources. Traffic is monitored at computer entry points known as ports, where information is exchanged with external devices.


Also Read | Cybersecurity Threats, Attacks and its Types


How does the Firewall Work?


Within a private network, firewalls filter network traffic. Based on a set of rules, it determines which traffic should be allowed or restricted. Consider the firewall to be a gatekeeper at your computer's entry point, allowing only trusted sources (or IP addresses) to enter your network.


A firewall only accepts incoming traffic that has been configured to accept it. It distinguishes between legitimate and malicious traffic and allows or blocks specific data packets based on predefined security rules.


These rules are based on various aspects of the packet data, such as their source, destination, content, and so on. To prevent cyberattacks, they block traffic from suspicious sources.


Various types of firewalls can read data packets at different network levels. You will now proceed to the next section of this tutorial and learn about the various types of firewalls.


Why use a Firewall?


Firewalls are mostly used to protect against malware and network-based attacks. They can also aid in the prevention of application-layer attacks. These firewalls serve as gatekeepers or barriers. 


They track every attempt to connect our computer to another network. They will not allow data packets to pass through unless they are coming or going from a user-specified trusted source.


Firewalls are designed to detect and counter-attacks across the network as quickly as possible. They can use rules to protect the network and perform quick assessments to detect any suspicious activity. In a nutshell, we can use the firewall as a traffic controller.


The following are some of the significant risks of not having a firewall :


  1. Open Source


When a computer is not protected by a firewall, it allows unrestricted access to other networks. This means it accepts any type of connection that comes through someone. It is not possible to detect threats or attacks coming through our network in this case. Without a firewall, we expose our devices to malicious users and other unwelcome sources.


  1. Data Loss or Compromise


Without a firewall, we make our devices available to anyone. This means that anyone with access to our device, including the network, can take complete control of it. Cybercriminals can easily delete our data or use our personal information in this case.


  1. Network Outages


Without a firewall, anyone could gain access to our network and shut it down. We may have to invest valuable time and money to get our network back up and running. As a result, it is critical to use firewalls to protect our network, computers, and data from intruders.


Also Read | Network Security: Types, Advantages and Disadvantages


Functions of Firewall


The firewall functions as a gatekeeper. It examines every attempt to gain access to our operating system and blocks traffic from unknown or unidentified sources.


We can think of the firewall as a traffic controller because it acts as a barrier or filter between the computer system and other networks (such as the public Internet). 


As a result, the primary function of a firewall is to secure our network and information by controlling network traffic, preventing unwanted incoming network traffic, and validating access by assessing network traffic for malicious things like hackers and malware.


Most operating systems (for example, Windows OS) and security software include firewall support. As a result, it's a good idea to make sure those options are enabled. Furthermore, we can configure the system's security settings to be automatically updated whenever new information becomes available.


Firewalls have become extremely powerful, with numerous built-in functions and capabilities:


  1. Network Threat Defense


  1. Control over applications and identities


  1. Support for Hybrid Cloud


  1. Scalable Efficiency


  1. Control and management of network traffic


  1. Validation of Access


  1. Observe and Report on Events


Also Read | What is Targeted Ransomware?



Types of Firewall


There are two types of firewalls based on what they protect: network-based and host-based. Network-based firewalls, which are frequently hardware, protect entire networks. Host-based firewalls, which are frequently software, protect individual devices known as hosts.


The following are the main types of firewall when categorizing by filtering method:

Types of Firewall :1. Firewalls with packet filtering 2. Stateful inspection firewalls 3. Next-generation firewalls 4. Application layer and proxy Firewall

Types of Firewall


  1. Firewalls with packet filtering


A packet's source and destination addresses, protocol, and destination port number are all checked as it passes through a packet-filtering firewall. If a packet does not comply with the firewall's rule set, it is dropped and not forwarded to its destination. 


For example, if a firewall rule is configured to block Telnet access, the firewall will drop packets destined for Transmission Control Protocol (TCP) port number 23, which is where a Telnet server application would be listening.


Although the source and destination port numbers are obtained from the transport layer, a packet-filtering firewall operates primarily on the network layer of the OSI reference model. It examines each packet independently and has no idea whether any given packet is part of an existing stream of traffic.


Because it processes each packet in isolation, the packet-filtering firewall is vulnerable to IP spoofing attacks and has been largely replaced by stateful inspection firewalls. Firewalls with strong inspection capabilities


  1. Stateful inspection firewalls


Stateful inspection firewalls, also known as dynamic packet-filtering firewalls, examine both incoming and outgoing communication packets over time. This type keeps track of all open connections in a table. 


When new packets arrive, it compares the information in the packet header to the state table (its list of valid connections) to determine whether the packet is part of an existing connection. If it is, the packet is allowed to pass without further inspection. If the packet does not match an existing connection, it is evaluated using the new connection rule set.


Stateful inspection firewalls are very effective, but they are vulnerable to denial-of-service (DoS) attacks. DoS attacks work by exploiting established connections of this type generally assumed to be safe.


  1. Application layer and proxy Firewall


This type of firewall is also known as a proxy-based or reverse-proxy firewall. They provide application-layer filtering and can examine the payload of a packet to distinguish valid requests from malicious code disguised as a valid data request.


At the application layer, packet-filtering and stateful inspection firewalls are ineffective. Because this type examines the payload's content, security engineers have more granular control over network traffic.


When this type is hosted on a proxy server, it makes it more difficult for an attacker to determine the location of the network and adds another layer of security. Both the client and the server are forced to route the session through an intermediary – the proxy server that hosts an application layer firewall.


The ability to block specific content, such as known malware or specific websites, and recognize when certain applications and protocols, such as Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), and domain name system (DNS), are being misused is the primary benefit of application-layer filtering.


Application layer firewall rules can also be used to restrict file execution or data handling by specific applications.


  1. Next-generation firewalls


This type combines the previous types with additional security software and devices. The advantage of an NGFW is that it combines the strengths of each type while covering the weaknesses of each type.


The need for a multilayer approach has resulted in the development of NGFWs. A next-generation firewall (NGFW) combines three key assets: traditional firewall capabilities, application awareness, and an intrusion prevention system (IPS).


NGFWs, like the addition of stateful inspection to first-generation firewalls, add context to the firewall's decision-making process. 


NGFWs combine traditional enterprise firewall capabilities, such as Network Address Translation (NAT), Uniform Resource Locator (URL) blocking, and virtual private networks (VPNs), with quality of service (QoS) functionality and features not typically found in first-generation products.


NGFWs support intent-based networking by incorporating SSL and SSH inspection, as well as reputation-based malware detection. The use of an NGFW or any firewall in conjunction with other devices is referred to as unified threat management (UTM).


Also Read | Content Delivery Network (CDN)



Advantages of Firewall


Understanding the benefits of firewall security is the first step toward assisting your company's safe growth in the ever-changing digital age.


  1. Monitors Network Traffic: The ability to monitor network traffic is the foundation of all firewall security benefits. By monitoring and analyzing network traffic, firewalls leverage pre-established rules and filters to keep your systems protected. 


  1. Stops virus attacks: The ability to control your system's entry points and stop virus attacks is one of the most visible benefits of firewalls. Depending on the type of virus, the cost of damage from a virus attack on your systems could be immeasurable.


  1. Avoids hacking: Unfortunately, the trend of businesses shifting to digital operations invites thieves and bad actors to follow suit. With the rise of data theft and criminals holding systems hostage, firewalls have become even more important in preventing hackers from gaining unauthorized access to your data, emails, systems, and other information.


  1. Spyware removal: Stopping spyware from gaining access and infiltrating your systems is a much-needed benefit in a data-driven world. Firewalls are an important barrier against malicious programs.


  1. Promotes Privacy: The promotion of privacy is an overarching benefit. Upgraded data-protection systems can also provide a competitive advantage and a selling point to customers and clients.


Also Read | What are Ethical Hacking and its Phases


The purpose of a firewall is to keep unauthorized connections and malicious software out of your network. Unwanted traffic can enter a network through software, hardware, or software-based cloud methods. As a result, the firewall must leave its imprint on all possible network fronts vulnerable to external attacks. 


A firewall is a cybersecurity tool that protects systems when they are connected to the internet. With so much malicious content floating around the internet and the exponential rise in cyber threats and cybercriminals, it is critical to keep systems secure. As a result, selecting the right type of firewall that meets the organizational requirements is critical to effectively protecting the systems.

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