A firewall is a cybersecurity tool used to prevent unauthorized access to your private device or network. It could refer to any software or hardware that checks the data and traffic coming in and going out of a network to ensure they comply with cybersecurity rules. Firewalls can also include what is known as an intrusion detection system (IDS), which additionally blocks malicious traffic while allowing legitimate and authorized traffic access to a network. Basically, a firewall acts as a barrier between a trusted private or internal network and an untrustworthy external network. Firewalls are also used to securely merge corporate networks through site-to-site virtual private networks (VPNs).

A firewall can offer different levels of protection based on the user's needs. Firewalls are used in enterprise and personal settings and are usually pre-installed in most operating systems and devices since they play a critical role in ensuring network safety. Some firewalls are more advanced than others ⁠— if your built-in firewall only offers basic protection, you can turn to a third-party firewall application to enhance the safety of your device or network.

Why do you need a firewall?

The moment a device connects to the internet or any external network, it becomes vulnerable to malware, ransomware and other cyberthreats. An unprotected device or network can be easily exposed by cybercriminals leading to hacking, identity theft and other forms of online fraud. Hence, it's useful to monitor your network traffic to ensure it's safe. A firewall offers proactive protection against cyberthreats by sniffing out potential dangers and protecting you against them, allowing you to surf the internet with a greater level of security.

Typically, a firewall establishes one or more checkpoints to vet the data and traffic moving in and out of your network. Think of it as the “wall” around your house or apartment building with one or more pre-designated entry and exit points or gates. Just as these gates allow you to let in trustworthy people while keeping out thieves and other intruders, a firewall allows you to interact with safe actors online or on external networks while allowing you to block malware and other harmful actors. Furthermore, a firewall may also allow you to restrict access to certain parts of a network just like the door to a room does in your house.

Benefits of using a firewall

The primary benefits of using a firewall are:

• It allows you to actively monitor your network and manage access.
• It protects your network against spyware, hackers and other cyberthreats.
• It protects the privacy of a device or network.
• It allows you to set and implement security policies and rules.

Types of firewalls

Firewalls can have different structures, functionality and traffic-filtering methods. Here are a few common types of firewalls.

Packet filtering firewalls

These operate at junction points like routers and switches, but this can also be on individual computers (e.g., macOS has a built-in packet filtering firewall). They check data packets to ensure they meet certain criteria. If a data packet passes the test, it is allowed into the network. Otherwise, it's not. The criteria for testing may include established cybersecurity rules and protocols, source and/or destination address or the port being used.

Proxy-level or application-level firewalls

Instead of operating through junctions like routers and switches, these firewalls operate at the level of applications. They use an application's pre-configured policies to determine what messages to send to and from an app.

Stateful inspection firewalls

These firewalls evaluate data packets based on their database of packets that were previously successful in passing through the firewall. These offer greater security than packet filtering firewalls by monitoring all activity within a network based on rules and contexts of previous connections and packets. However, stateful inspection firewalls can take a toll on overall network performance.

Next-generation firewalls (NGFWs)

These firewalls combine the previously described methods to boost network security. They monitor packets at an application level while conducting quick network assessments to raise alerts for any suspicious or invasive activity. NGFWs offer standard firewall capabilities as well as advanced firewall capabilities to help effectively deal with evolving cyberthreats.

Best practices for firewalls

Managing a firewall can be a challenging task for administrators. You must strike the right balance between security enhancement and uncompromising network performance. Here are a few best practices that will help you effectively manage your firewall.

• Update regularly: Ensure your firewall software is updated regularly. Like any other software on your network, it is continually enhanced to ensure continued protection.
• Centralize firewall management: This is necessary if you use multiple firewalls to achieve greater security within your network. A network monitoring tool will give you a comprehensive view of all your firewalls to help you manage them more effectively.
• Optimize security rules: The effectiveness of your firewall depends on the rules and conditions you set for it. Eliminate all unessential, conflicting, obsolete and redundant rules. Address all errors to prevent your firewall from malfunctioning.
• Establish a plan for changes: Given the constantly evolving nature of threats, you will have to alter your firewall from time to time. Make your transition process easy, seamless and secure by establishing a plan for firewall change management.
• Use access management and documentation: Control who has access to the network and who can make changes to your firewall configurations. Log all changes for audit and compliance so that unwanted changes can be easily identified and rectified.
• Regular audit: This will ensure your firewall configurations are effective and help you identify any unauthorized changes. It will help you manage risks arising from firewall migration activities, bulk changes, multivendor firewalls, etc.

A security tool for the evolving threat landscape

A firewall can protect your devices and network against malicious software and actors by monitoring its traffic and activities. With cyberthreats constantly increasing and evolving, a firewall is an important cybersecurity tool to keep your network safe and private. Ensure your firewall is up-to-date and manage it well to combat malware, phishing attacks and other cyberthreats.