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firewall; network security

What is a Firewall? Its Role in Network Security

Aaron Foglia
4 min read
Feb 27, 2023 10:52:08 AM
This post covers:Your Business. Secure. | Managed IT

Updated January 29, 2024

Securing your network from various threats has become an essential part of maintaining a safe online environment. One of the most crucial components of network security is a firewall. But what exactly is a firewall, and how does it work? We take a closer look at firewalls, exploring what they are, how they work, and why they are indispensable in the realm of cybersecurity.

What is a firewall?

A firewall is the first line of defense in protecting your network from outside threats, and firewalls have been an integral part of network security for over 25 years – almost as long as computers have been a part of the everyday business world.

More specifically, a firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It acts as a barrier between trusted internal networks and untrusted external networks such as the internet. Firewalls can be either hardware or software-based, but they all serve the same purpose: to block unauthorized access while permitting outward communication.

How does a firewall work?

A firewall essentially acts as a gatekeeper for your computer or network, allowing only safe data to pass through. Think of a bouncer monitoring the door day and night, checking credentials, and determining who goes in and out.

More technically, think of it as a programmable filter between your computer or network and the internet. You can program this filter to block specific types of content, like certain websites or services. When information attempts to enter your system from the internet, it must first pass through this filter. If it doesn't meet the criteria you've set up, it's not allowed in.

Firewalls work by inspecting packets (small chunks of data) coming into your system from the internet. They compare these packets against their database of rules – if they find a match that says "block," then that packet isn't allowed through.

The role of a firewall in network security

 Firewalls play a vital role in network security. They provide the first line of defense against cyber threats by blocking unauthorized access to your network. They can also be used to segment a network into secure zones, each with its own protection policies and controls.

Firewalls are particularly effective at preventing attacks that exploit vulnerabilities in an operating system or application. By blocking all traffic that doesn't meet specific criteria, they prevent malicious software from entering and spreading within your network.

In addition to blocking unwanted traffic, firewalls can also monitor network activity. They log all attempts to enter your network, successful or not. This information can be used to identify patterns and detect suspicious behavior.

Types of firewalls

There are several types of firewalls including hardware firewalls, software firewalls, and cloud-based firewalls. Each type uses different methods for controlling traffic flow, blocking certain types of traffic, and analyzing packets for potential threats.

Packet-filtering firewalls 

This is a management program that can block network traffic IP protocol, an IP address, and a port number. It is the most basic form of protection and is meant for smaller networks. While helpful, it also has limitations. You need additional protection to distinguish between friendly and malicious web traffic.

Proxy service firewalls 

This system filters messages at the application layer. It acts as a middleman between your internal network and outside servers on the web. It’s also known as a gateway firewall.

Stateful multi-layer inspection (SMLI) firewalls

The SMLI has standard firewall capabilities and keeps track of established connections. It uses dynamic packet filtering to monitor active connections and determine network packets that can pass through the firewall. It monitors all activity within a network and makes decisions based on defined rules and the context of previous connections and packets.

Unified threat management (UTM) firewalls

This program combines the functions of the SMLI firewall with intrusion prevention and antivirus. Additional services like cloud management may be included under UTM.

Network address translation (NAT) firewalls

A NAT firewall can assess internet traffic and block unsolicited communication. It only accepts inbound web traffic if a device on your private network solicited it.

Virtual firewalls

This is an appliance used in a cloud-based system, both private and public. This type of firewall will assess and manage internet traffic over both physical and virtual networks.

Next-generation firewalls (NGFW) 

Next-generation firewalls are more sophisticated and have more levels of security, going beyond standard packet filtering to inspect a packet’s contents and source. NGFW can block more sophisticated and evolving security threats like advanced malware and protection from questionable sites.

Why are firewalls necessary?

Protection against unauthorized access

The primary and most crucial role of a firewall is to shield a network from unauthorized access. By scrutinizing incoming and outgoing traffic, firewalls prevent malicious entities from infiltrating the network and gaining unauthorized access to sensitive data or resources.

Defense against cyber threats

Cyber threats come in various forms, from malware and viruses to sophisticated hacking attempts. Firewalls act as the first line of defense, thwarting these threats by identifying and blocking malicious traffic. This proactive approach is essential in preventing potential security breaches that could compromise the integrity of the entire network.

Regulatory compliance

Many industries are subject to stringent regulatory requirements concerning data protection and privacy. Firewalls play a pivotal role in ensuring compliance with these regulations by implementing security measures that safeguard sensitive information and prevent unauthorized disclosure.

Secure remote access

With the rise of remote work, secure access to internal networks from external locations has become a necessity. Firewalls facilitate secure remote access through Virtual Private Networks (VPNs) and other technologies, ensuring that employees can connect to the corporate network without exposing it to external threats.

Enhancing firewall security

While firewalls are an essential part of any network security strategy, they're not infallible. Cybercriminals are constantly developing new techniques to bypass firewall protections. Therefore, it's important to regularly update your firewall's rules and security policies to keep up with the latest threats.

In addition to maintaining your firewall, it's also crucial to use other security measures in conjunction with it. These might include antivirus software, intrusion detection systems (IDS), and regular system updates.

Assessing your network security firewall

In conclusion, a firewall is a critical component of any network security. Firewalls are the unsung heroes of cybersecurity, standing as formidable guardians against a myriad of digital threats. Their ability to monitor, filter, and control network traffic is instrumental in maintaining the integrity and security of modern digital infrastructures. As technology continues to advance, the role of firewalls will only become more pivotal in preserving the confidentiality, integrity, and availability of data in an interconnected world. Organizations need to recognize this and invest in robust firewall solutions to fortify their defenses against the ever-evolving landscape of cyber threats.

For many organizations who aren’t confident about their current firewall security, partnering with a managed security service provider to complete a security assessment can be a good first step.


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