Most of us may have heard the term and know it’s related to security in some way, but do you really know what a firewall is? Traditionally, firewalls were built to keep danger at bay; they were doors (or walls) that blocked fire from entering another area, hence the name firewall. When you’re thinking about online security, modern-day hardware and software firewalls are similar. They act as barriers to prevent unauthorized access to your personal information.

Firewall Definition in Network Security

A firewall is a hardware device or software program that filters the information moving between your devices and the internet, examining each piece of data to determine whether it should be allowed or blocked. This helps protect your personal information and devices from unauthorized access and online threats.

The Purpose of a Firewall

A firewall acts as a barrier between your devices and potential online threats. By inspecting incoming and outgoing traffic, firewalls help stop malicious programs, hacker attempts, and other unwanted activity before it reaches you.

Where Firewalls Are Used

You’ll find firewalls built into many home routers, safeguarding every device on the network. Software firewalls run directly on laptops and mobile devices, providing protection wherever you connect, whether you’re at home, at a café, or on public Wi‑Fi.

Firewall Benefits

Firewalls offer an essential layer of security by monitoring traffic in real time and blocking suspicious behavior. They complement other protections, helping reduce the risk of attacks, malware, and unauthorized access to your personal data.

How do Firewalls work?

Firewalls work by examining the data that moves between your devices and the internet and deciding what should be allowed through. They rely on predefined security rules to filter this traffic, blocking anything that appears unsafe or unauthorized. Whether built into your home router or installed as software on your device, a firewall constantly monitors network activity to keep threats out.

Hardware firewalls act as a first line of defense, screening traffic before it reaches your devices. Software firewalls take a closer look at the connection on the device itself, helping intercept malicious programs or suspicious behavior before it can leave or enter your system. Together, they create layered protection that helps guard your personal data from online threats.

Types of Firewalls

Network Firewalls

Network firewalls sit at the boundary between trusted and untrusted networks, as in your internal network and the internet. They inspect traffic based on predefined rules to block unauthorized access and maintain network integrity. They can exist as hardware, software, or a combination of both.

Stateful Firewalls

Stateful firewalls track active connections and make decisions based on the context of the traffic, not just individual packets. By understanding whether a packet belongs to an established and legitimate session, they offer stronger protection than basic packet‑filtering systems.

Proxy‑Based Firewalls

Proxy (application‑level) firewalls act as intermediaries between users and the Internet. They inspect full-application-layer traffic, such as HTTP requests and email commands, to identify and block malicious content. They also hide internal IP addresses to improve privacy.

Next‑Generation Firewalls (NGFW)

NGFWs go beyond traditional filtering by combining deep packet inspection, intrusion prevention, application awareness, and, in some cases, encrypted traffic inspection. This allows them to identify more advanced threats and enforce more granular security policies.

Web Application Firewalls (WAF)

A Web Application Firewall protects web applications, APIs, and online services from attacks that target application‑layer vulnerabilities, such as SQL injection, cross‑site scripting, or malicious HTTP requests. WAFs are designed specifically to guard modern web workloads that traditional firewalls may not fully cover.

Firewall‑as‑a‑Service (FWaaS)

FWaaS delivers firewall capabilities through the cloud, allowing organizations to apply uniform security policies across distributed users, devices, and locations. Instead of deploying hardware, security is managed centrally and scales easily across remote workforces or multi‑site environments.

Hardware vs. Software Firewalls

Hardware firewalls, such as those included with some routers, are usually a good first line of defense against outside attacks, and they require little to no configuration. The one downside of using only a hardware firewall is that it only protects you if you are at home. So if you take your computer to a cafe or on a trip, it’s no longer protected by the home firewall.

Fortunately, software firewalls can catch these kinds of threats because they are running on your computer and can take a closer look at the network traffic. This allows them to intercept a malicious program before it leaves your computer.

Firewall Configuration Criteria

Firewalls make decisions based on a predefined set of rules that determine which traffic is allowed, blocked, or closely inspected. These rules often consider attributes like source and destination IP addresses, port numbers, protocols, and application‑layer behaviors to filter out suspicious or unauthorized activity.

Modern firewalls may also use more granular criteria to strengthen security and better detect malicious traffic, such as user identity, time of day, or recognized threat patterns. These configurable elements help ensure the firewall adapts to your environment, reinforces network policies, and maintains consistent protection against evolving threats.

Tips for Greater Security Online

Now that you know the purpose of firewalls, follow these tips for greater security online:

  • Make sure you are using a router that includes a firewall as a first layer of protection
  • Turn off file-sharing and printer-sharing features if you don’t need them
  • Use common sense, don’t click on links or open attachments from people you don’t know, you could unknowingly be giving them access to your device

While the bad guys may always be looking to do harm, just remember that we all need to be vigilant about protecting ourselves and our devices, which in turn helps protect everyone else. This is a good reminder for us all as we celebrate National Cyber Security Awareness Month.