What is Network Perimeter Security?

Network perimeter security involves monitoring and controlling network traffic between internal and external environments. Network firewalls define the perimeter and specify the types of traffic permitted to enter and leave the network. Organizations also commonly define demilitarized zones (DMZs), which isolate public-facing services, such as corporate web servers and email servers, from the rest of the organization’s networks.

Perimeter security is essential to the security of the traditional network, where all corporate data and assets lie within the perimeter. This article explores how perimeter security works, its shortcomings, and how solutions like the Cato SASE Cloud Platform modernize network security.

Understanding Network Perimeter Security

Traditionally, the network perimeter defined the boundary between an organization’s internal IT assets and the public Internet. A firewall sits at this boundary and uses predefined rules to decide whether traffic should be allowed to pass through or blocked.

Under this model, all of an organization’s assets are inside the perimeter; however, this has changed in recent years. With the rise of cloud computing and remote work, trusted assets and users are now outside the traditional perimeter, forcing a new approach to network security.

Traditional Definition

The perimeter security model was originally conceived for office-based environments. If all of an organization’s employees were on-site and its IT assets were located in an on-prem data center, then the organization’s connection to its Internet Service Provider (ISP) separates its private network from the public Internet.

In this office-based, pre-cloud environment, perimeter security solutions are deployed at the edge of the corporate network, right before the edge router. Since all corporate network traffic passes through this location, the firewall has full control over the traffic passing through it.

What It Protects

Network perimeter security was designed to protect all of an organization’s internal systems and resources. These include:

• Internal servers
• API endpoints
• Data
• SaaS access
  

An organization may also define a DMZ to protect its public-facing assets. These include:

• Web server
• Email server
• DNS server

Why Perimeters Are No Longer Static

The traditional network perimeter applied to office-based environments, where all corporate IT assets sat within the perimeter. However, this perimeter was disrupted due to digital transformation, such as:

• Hybrid Work: Employees working remotely access corporate data and internal services from outside of the traditional perimeter. While virtual private networks (VPNs) allow an organization to treat this traffic as internal, devices may carry malware in – or data out – of the organization’s network.
• Mobile Devices: Employees increasingly work from mobile devices, which are connected to mobile networks rather than the corporate Wi-Fi. This exposes them to additional cyber threats and puts them at risk of loss or theft.
• Cloud Adoption: Cloud computing moves an organization’s cloud-based data and services outside of the traditional perimeter. This makes perimeter security more complex as internal traffic between on-prem and cloud environments passes over the public Internet, and remote workers may access cloud resources directly via the Internet.

Key Components of Network Perimeter Security

Historically, network perimeters used firewalls and IDS/IPS to inspect and secure network traffic, while VPNs provided remote access to corporate resources. DMZs offer additional protection by isolating high-risk, public-facing resources from the rest of the internal network.

Firewalls and NGFWs

Firewalls define the network perimeter by filtering traffic entering and leaving the network. Over time, the original stateless firewalls have evolved to the next-generation firewall (NGFW), which performs deeper traffic inspection and understands the various types of application traffic. This allows an organization to apply more granular security policies and filter traffic at the application level rather than the protocol level.

VPNs

VPNs are designed to permit remote work while maintaining the traditional perimeter security model. Remote workers’ traffic is encrypted as it passes over the public Internet and decrypted by a specific VPN endpoint. While VPNs enable traditional perimeter security, they have their limitations. For example, remote users are granted unrestricted access to the corporate network, and VPNs introduce additional management complexity and reduce network visibility.

IDS/IPS

Intrusion detection and prevention systems (IDS/IPS) are designed to identify potential threats, such as malware or credential stuffing, against an organization’s systems. IDS can only generate alerts for suspicious traffic, while IPS can block attempted attacks if deployed in-band. IDS/IPS capabilities are often deployed at the network perimeter to stop malicious content from entering the organization’s environment.

DMZs

A DMZ is a network segment that is isolated from the rest of the organization’s private network and hosts public-facing resources like web servers. Its role is to reduce the risk that an attacker who compromises the public service will be able to pivot to internal systems and the more valuable data that they contain.

Challenges in Perimeter Security

Perimeter security models don’t account for internal threats, cloud, and remote work. This exposes an organization’s vulnerability to cyberattacks and complicates regulatory compliance.

Internal Threats and Lateral Movement

The perimeter security model assumes that anything inside the network is legitimate, which creates a false sense of security. If an attacker breaches the perimeter – via stolen credentials, vulnerability exploitation, or similar means – then they have unrestricted access to the corporate network.

Lack of Visibility

Firewalls and other security tools provide insight into the traffic that passes through them. However, if an organization has only perimeter-based defenses, it can only monitor traffic entering and leaving the network. Without visibility into internal network traffic, an organization is blind to attackers who have breached the perimeter. This may permit them to move laterally from their initial access point to their final objective without detection.

Perimeter Drift in Cloud Environments

When organizations adopt cloud computing, they break the traditional perimeter model since some of their assets are no longer on-prem and accessible from the public Internet. This makes perimeter-based security more complex and inconsistent because the organization needs to equally secure all of its new network perimeter. Otherwise, an attacker who breaches a weakly-defended portion of the network can move laterally to access other systems from behind the organization’s perimeter defenses.

Modern Alternatives to Traditional Perimeters

As networks evolve, modern network security solutions have emerged to provide the visibility and control that perimeter-based tools lack. The zero trust security model, implemented via zero trust network access (ZTNA) solutions, offers more granular visibility and control and supports modern corporate IT environments.

Zero Trust Architecture

Perimeter security models implicitly trust any entity within the perimeter. Zero trust moves away from this implicit trust, performing explicit verification of every access request. This model enables an organization to implement dynamic, least privilege access control. Users are only assigned the privileges that they need for their role, and these privileges are checked at the time of use, allowing the organization to rapidly change access controls if needed.

Microsegmentation

Network segmentation breaks the network into isolated segments, and microsegmentation takes this a step further by placing perimeters around individual assets and services. This helps to contain threats and limit lateral movement by providing visibility and control over all requests to services, regardless of their source and destination.

Zero Trust Network Access

ZTNA solutions implement microsegmentation to offer visibility and control over requests to individual resources. Requests to these resources are evaluated based on access controls and contextual factors to offer granular, case-by-case access management.

How Cato Networks Redefines Perimeter Security

Perimeter-based security is ineffective in the age of cloud computing, mobile work, and sophisticated cyberattacks. The Cato SASE Cloud Platform modernizes network security by converging network and security capabilities into a single, cloud-native solution, reducing network security complexity and challenges.

SASE Architecture

Secure Access Service Edge (SASE) converges a full network security stack with software-defined WAN (SD-WAN) in the cloud. By doing so, it eliminates the need for legacy perimeter appliances while ensuring that all network traffic is inspected for malicious content detection and policy enforcement. Additionally, converged security enhances efficiency and performance by performing multiple security functions within a single-pass engine.

Built-In ZTNA

The Cato SASE Cloud Platform includes ZTNA capabilities, enforcing zero trust access controls at each SASE point-of-presence (PoP). Organizations can define policy-based, least-privilege access controls and have them consistently applied across the corporate network for every internal and external request.

Real-Time Threat Protection

The Cato SASE Cloud Platform inspects traffic in the cloud and automatically identifies and blocks threats based on global threat intelligence. With full traffic visibility and cloud scalability, the platform offers enterprise-grade security with minimal performance impact.

FAQs About Network Perimeter Security

Why is perimeter security not enough anymore?

As companies adopt cloud computing, mobile devices, and hybrid work, sensitive data and IT assets are now located outside of the corporate network perimeter. Additionally, this model doesn’t account for insider threats that are already behind traditional controls.

What is a modern alternative to perimeter security?

Zero trust inspects all requests, regardless of their source and destination. With least-privilege access controls, an organization can granularly manage access to sensitive resources to minimize the risk of compromise.

How does Cato Networks help?

The Cato SASE Cloud Platform converges network and security functionality into a single solution. This integration ensures consistent, enterprise-grade security throughout the corporate network.

Bridging Traditional and Modern Network Security

While perimeter-based security controls are valuable, they’re not enough for security. Adopting modern security tools, such as Zero Trust and SASE, provide visibility and protection for resources outside of the traditional perimeter. The Cato SASE Cloud Platform offers converged security and networking functionality in a cloud-native solution.

Tired of juggling firewalls and VPNs? Discover how Cato Networks replaces legacy perimeter security with a unified SASE platform built for modern work. Request a demo to see how a converged, cloud-native platform can transform your network defense strategy.