What Are the Types of Firewalls and How Do They Protect Your Computer?

Firewalls are the primary layer of cybersecurity for preventing malicious network packets from entering your computer. However, there are various firewall types, and selecting the right one for your organization requires a good understanding of your specific security needs.

Identifying the correct type of firewall involves several considerations, including the size and budget of your business. It also considers the infrastructure architecture and technical skills of your security team.

Packet Filtering

Packet filtering is a firewall that determines whether incoming and outgoing data packets should be forwarded to their intended destination. It examines rules, protocols, ports, and destination addresses.

Unlike other types of firewall, it requires only one screening router to secure an entire network. This makes it a highly efficient and effective firewall technique because it accepts and rejects packets quickly based on their destinations, source ports, and IP addresses.

Another advantage of this type of firewall is that it operates transparently to users. While other firewall techniques require custom software, client machine setup, and user training or procedures, packet filters do not need any.

This is because they work autonomously without needing user cooperation. In addition, they are user-friendly and easy to incorporate into your network.

Some sites even have packet filtering capabilities built into their routers, which makes it an easy and cost-efficient way to improve security in your network.

However, there are some limitations to using this strategy in your network. For starters, it is only sometimes as secure as stateful inspection techniques and can be vulnerable to address spoofing. Also, it may need logging capabilities, which can be problematic for businesses that rely on traffic logging for compliance or reporting purposes.

Stateful Inspection

Stateful inspection is a technique used by many firewalls to monitor and keep track of established connections. Firewalls that use stateful inspection can block certain types of traffic that aren’t essential for the network.

With stateful inspection, firewalls analyze packet headers and payload information to determine whether a connection is safe or unsafe. This is called dynamic packet filtering, or DPF. It’s an advancement over static packet filtering, which only looks at packet headers and IP addresses.

This type of filtering can help protect a company from cyberattacks. It can also save money and prevent downtime.

A big advantage of stateful inspection is that it can monitor connection information from multiple sources, making it easier to detect attacks on the network. This information can include the destination port, the source and sequence numbers of any metadata, and a combination of other information.

The firewall stores this information in its state table and updates it as more data enters. This helps the firewall know which connections to allow and which to drop, helping to protect the network from attacks.

However, one major downside of stateful inspection is that it can be a performance detriment compared to a traditional packet filter. This is because the maintained tables and the logic used to parse access lists take up processor power and memory space. This may be a problem for large organizations or if many users are accessing a given application.

Application Layer

An application layer firewall is a network security appliance that controls and filters data sent by applications on your internal network. These firewalls allow or block traffic based on predefined rules.

These devices work at the application level of the TCP/IP stack and may intercept all packets traveling to or from a specific application, such as a web browser, e-mail server, or FTP client. They can also block unauthorized packets and drop packets the sender does not acknowledge.

The firewall can also analyze each message’s header to determine if it contains suspicious or malicious information or violates network policies. This helps detect and prevent attacks such as spam and spoofing that might otherwise be impossible to see at the network or transport layers of the OSI model.

A firewall can also examine the contents of a message to see if it contains any suspicious or malicious information, such as a character string not found in standard messages. This can be done through an advanced technology called ALF (Advanced Language Filtering).

The firewall can also use information spanning multiple connections for one host, such as the user’s IP address or the ports they’re using to connect, to decide what packets to allow and block. This is a more advanced and complex process than traditional firewalls, which typically make decisions based only on source/destination IP addresses and ports.


Next-generation firewalls (NGFW) build on the capabilities of traditional firewalls to provide deeper packet inspection, application control, intrusion prevention, and web content filtering. They also have cloud-delivered threat intelligence that helps identify and block threats before they enter your network.

The primary difference between NGFWs and traditional firewalls is that NGFWs operate at the application layer of the TCP/IP protocol stack, giving them visibility into network traffic that traditional firewalls cannot see. This allows them to decrypt encrypted network packets and inspect them for malicious or unauthorized data.

Another key difference is that NGFWs integrate multiple security tools, such as intrusion prevention systems and antiviruses, with their firewall services to speed up processing. This reduces the complexity of managing various unrelated security products and makes NGFWs more affordable than traditional firewalls.

NGFWs also support multi-layer protections like VPN, network address translation, and packet filtering. This enables them to use dedicated network bandwidth as security protocols, and devices come online while also allowing them to manage traffic efficiently by applying granular rules.

In addition, NGFWs are often better at identifying new threats than traditional firewalls, which can become obsolete if they are not updated to include the latest security technology. Moreover, they provide more comprehensive protection than stateful firewalls, which can only block or allow packets based on IP address, port number, and protocol.

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