Skip to content Skip to navigation Skip to footer

What Is a Perimeter Firewall?

A perimeter firewall refers to a security application that defends the boundary between a private network and a public network. Its goal is to prevent unwanted or suspicious data from entering the network. It protects against cyberattacks and other malicious traffic by scanning each data packet that tries to enter the network. 

A perimeter firewall can also act as a proxy service, an intermediary between users and the internet, that allows greater access control by an administrator. As a perimeter firewall examines the content of the data packet, it can tell if it contains a threat based on the information in the packet’s header and the payload of the packet itself. 

A perimeter firewall can filter both internal and external traffic. Internal traffic is traffic that originates from within your network and travels between users, internal networks, and devices. External traffic is traffic that comes from outside the network from the internet. External traffic presents greater risks because there are millions of threats across the internet that can target your organization.

Network Perimeter

The network perimeter works as both a barrier and an entry point to the internet or an internal network to which it is connected. The perimeter of a network needs to be a secure boundary against cyberattacks.

The network perimeter can be protected by a perimeter device such as a firewall, intrusion prevention system (IPS), intrusion detection system (IDS), or a virtual private network (VPN). Because of the introduction of virtualization and cloud computing, the network perimeter has changed over time. Virtualization and cloud computing architectures can be appended to your primary network, thereby extending its perimeter while also increasing the size of the area you have to protect from threats.

 Basic Functions of a Perimeter Firewall

A perimeter firewall is your network’s first line of defense. It examines each data packet that attempts to enter the network, checking for signs of malware or data that may indicate it is being used by cyber criminals for a denial-of-service (DoS) attack and other types of attacks. Using information from cyber intelligence systems, the firewall can recognize the signatures of specific threats. 

A next-generation firewall (NGFW) on the perimeter also makes use of artificial intelligence to scour the data packet for threats a regular firewall may miss.

Perimeter Firewall Risks

A perimeter firewall can possibly be infiltrated by unknown devices that connect from outside the network, including the laptops and mobile devices of users and employees. Also, as businesses migrate their operations to the cloud, they have to make sure they adapt their defense to protect their infrastructure against attackers who target cloud architectures found in data centers, Software-as-a-Service (SaaS) providers, and other cloud computing systems. 

In addition, when a company opens up its network to interface with another through the internet, it can also possibly allow malicious code or an unauthorized individual into their network. Also, insider attacks may not be detected by a perimeter firewall because the malicious data originates from behind the firewall. Therefore, a firewall should be just one component of a larger network security plan.

How Does a Network Perimeter Firewall Work?

A perimeter firewall protects a network from unwanted traffic by inspecting all traffic before it is allowed to enter. For example, if an organization does not want its employees to access a social media site like Instagram or Facebook, the perimeter firewall can be programmed to block it. 

The firewall also blocks illicit traffic that originates from within the network as it tries to exit the system. 

Static Packet Filtering

Static packet filtering is filtering data using information contained within the packet’s header. Inside the header is information regarding where the packet is coming from, where it currently is, and where it intends to go. If the header information contains data from an unwanted site, for example, the firewall can block it.

Stateful Inspection

Stateful inspection, also known as dynamic packet filtering, makes a record of outgoing traffic. It then only allows traffic to go through if it matches a previous request.

Data Center Firewall vs. Perimeter Firewall

A data center firewall is designed to protect virtual networks hosted within a data center. There is a growing need for data center firewalls because as more and more businesses use data centers, threat actors continue to shift their focus toward these targets.

Data center firewalls are different from network perimeter firewalls in that they are built to protect virtual machines. They are also designed for agility unique to data centers, giving administrators the freedom to reallocate virtual resources as they see fit without breaking firewall policies. 

The FortiGate data center firewall (DCFW) solution improves network security without affecting performance. This is accomplished using high-speed interfaces that provide throughput starting at 50 Gbps and surpassing 1 Tbps. Even at these high speeds, the FortiGate DCFW can perform detailed inspections of each data packet that attempts to pass through.

Network Perimeter Security Is Your First Line of Defense

Using next-generation firewalls (NGFWs) gives you deeper packet inspection capabilities because malware inside the packet’s contents—not just signs of malware in the header—can be detected. It is important to not only secure the perimeter of your network but the interior as well, particularly because a threat introduced by a connected user can work its way through your network without being detected by a perimeter firewall. 

The FortiGate NGFW comes in several permutations, all of which are designed to protect both the perimeter and inside of your network. These include the 7060E with 80 Gbps of threat protection, 7040E that filters out threats at 40 Gbps, 7030E with 35 Gbps, and the 5001E, which provides 13.5 Gbps of protection. Fortinet has been recognized as a leader in Gartner’s Magic Quadrant for Network Firewalls.