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Firewall Definition

A firewall is a network security solution that protects your network from unwanted traffic. Firewalls block incoming malware based on a set of pre-programmed rules. These rules can also prevent users within the network from accessing certain sites and programs.

Firewalls are based on the simple idea that network traffic from less secure environments should be authenticated and inspected before moving to a more secure environment. This prevents unauthorized users, devices, and applications from entering a protected network environment or segment., Without firewalls, computers and devices in your network are susceptible to h ackers and make you an easy target for attacks.

While an advanced firewall can no longer single-handedly defend a network against today’s complex cyber threat landscape, these devices are still considered to be the foundational building block for creating a proper cybersecurity system. As part of the first line of defense against cyberattacks, firewalls offer essential monitoring and filtering of all traffic, including outgoing traffic, application-layer traffic, online transactions, communications and connectivity— such as IPSec or SSL VPN— and dynamic workflows. Proper firewall configuration is also essential, as default features may not provide maximum protection against cyberattacks.

As the digital landscape grows more complex due to more devices, users, and applications crossing through the network perimeters – especially due to the growing volume of IoT and end user devices – and less overall centralized control from IT and security teams, companies are becoming much more vulnerable to cyberattacks. Therefore, it is essential to understand how firewalls work, what different types are available, and which are the best for securing which areas of your network. 

What Does a Firewall Do?

Originally, firewalls were divided into two camps: proxy and stateful. Over time, stateful inspection became more sophisticated and the performance of proxy firewalls became too slow., Today, nearly all firewalls are stateful and divide into two general types: network firewalls and host-based firewalls.

A host-based or computer firewall protect just one computer, or "host,"  and are typically deployed on home or personal devices, often coming packaged with the operating system. Occasionally, though, these firewalls can also be used in corporate settings to provide an added layer of protection. Considering the fact that host-based firewalls must be installed and maintained individually on each device, the potential for scalability is limited.

Firewall networks, on the other hand, protect all devices and traffic passing a demarcation point, enabling broad scalability. As the name implies, a network firewall functions at the network level, OSI Layers 3 and 4, scanning traffic between external sources and your local area network (LAN), or traffic moving between different segments inside the network. They are placed at the perimeter of the network or network segment as a first line of defense and monitor traffic by performing deep packet inspection and packet filtering. If the content of the packets do not meet previously selected criteria based on rules that the network administrator or security team has created, the firewall  rejects and blocks that traffic. 

network firewall and host-based firewall differences

Why Are Network Firewalls Important?

Without a network firewall, network security is compromised, and your organization is wide open to bad actors who could steal or compromise your data or infect your network with malware. On the internet, a firewall is necessary to ensure all traffic is monitored efficiently.  Otherwise internet traffic could enter and exit your network unrestricted, even if it’s carrying malicious threats.

Network firewalls are foundational components of an organization’s security infrastructure. Their main job is to monitor incoming and outgoing traffic and either allow or block it. They help protect the network from threats such as:

  1. Malware
  2. Exploits
  3. Malicious websites

Some immediate consequences of a firewall breach are company-wide outages, which result in productivity loss. Longer term problems include data breaches and reputation damage. 

Various Types of Firewalls

What does a firewall do? The answer often depends on where it is and what it is supposed to protect. While all firewalls seek to protect your computer or network, there are different types of firewalls. What happens if you do not have a firewall depends on the attack surface the firewall is designed to shield you from. 

For example, if your personal computer does not have a firewall, viruses, malware, and hackers can have open access and even take over your device completely. In other instances, even if your computer is without a firewall, as long as the network it is attached to is protected, you can enjoy a degree of security because the firewall is still between your device and attackers on the internet.

Here are some of the different firewall types and their functions:

  1. Packet layer: A packet layer analyzes traffic in the transport protocol layer. At the transport protocol layer, applications can communicate with each other using specific protocols: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). The firewall examines the data packets at this layer, looking for malicious code that can infect your network or device. If a data packet is identified as a potential threat, the firewall gets rid of it.
  2. Circuit level: A firewall at the circuit level is positioned as a layer between the transport layer and the application layer of the TCP/Internet Protocol (TCP/IP) stack. Thus, they work at the session layer of the Open Systems Interconnection (OSI) model. In the TCP model, before information can be passed from one cyber entity to another, there needs to be a handshake. A circuit level firewall examines the data that passes during this handshake. The information in the data packets can alert a firewall to potentially harmful data, and the firewall can then discard it before it infects another computer or system.
  3. Application layer: An application layer firewall makes sure that only valid data exists at the application level before allowing it to pass through. This is accomplished through a set of application-specific policies that allow or block communications being sent to the application or those the application sends out.
  4. Proxy server: A proxy server captures and examines all information going into or coming out of a network. A proxy server acts like a separate computer between your device and the internet. It has its own IP address that your computer connects to. As information comes in or goes out of the proxy server, it is filtered, and harmful data is caught and discarded.
  5. Software firewalls: The most common kind of software firewall can be found on most personal computers. It works by inspecting data packets that flow to and from your device. The information in the data packets is compared against a list of threat signatures. If a data packet matches the profile of a known threat, it is discarded.
What are the five different types of firewalls?
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What Is a Firewall?

A firewall is a network security solution that protects your network from unwanted traffic. Firewalls block incoming malware based on a set of pre-programmed rules.

What are the types of firewall?

  1. Web Application Firewall
  2. Unified Threat Management Firewall
  3. Network Address Translation Firewalls
  4. Internal Segmentation Firewalls
  5. Next-Generation Firewalls

Why Are Network Firewalls Important?

Without a network firewall, network security is compromised, and your organization is wide open to bad actors who could steal or compromise your data or infect your network with malware.

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