Network Segmentation: All You Need to Know

TL;DR: Understanding Network Segmentation in Cybersecurity  

Network segmentation divides a network into smaller subnetworks to enhance security, control access, improve performance, simplify management, and aid regulatory compliance by isolating critical systems and data flows.  

The core function of network segmentation is to prevent lateral movement – in an era where 90% of organizations are currently exposed to at least one attack path, addressing flat network architectures with segmentation is critical.  

While network segmentation is key to bolstering cybersecurity defenses and accelerating threat containment, traditional segmentation strategies are struggling to match the speed and sophistication of modern cyber threats.  

What is Network Segmentation?

Network segmentation is a fundamental cybersecurity strategy that involves dividing a larger network into smaller subnetworks, or segments. Each segment functions as an isolated entity, with its own set of security controls and policies, creating boundaries that limit attackers’ ability to move laterally within the network.  

Common network segmentation methods include virtual local area networks (VLANs), subnets, access control lists (ACLs), internal firewalls, and physical separation of network infrastructure. 

By segmenting the network, administrators can: 

• Improve network performance 
• Control access to sensitive resources 
• Reduce the attack surface 
• Block lateral movement and better protect against sophisticated cyber threats 
• Streamline regulatory compliance  

Proper network segmentation enhances both the security and efficiency of network infrastructure. 

Types of Network Segmentation 

Common network segmentation approaches break into three categories: logical segmentation, physical segmentation, and perimeter-based segmentation.  

Logical Segmentation 

Logical segmentation uses approaches like VLANs, subnets, or software-defined networking (SDN) to create virtual boundaries within a single physical network. This allows different departments, teams, or applications to operate in separate segments with their own access controls and security policies, even if they share the same hardware. 

For example, VLANs can isolate user groups and prioritize traffic, while subnetting divides a network into smaller address spaces to control traffic flow.  

When to use logical segmentation:  

Logical segmentation is especially useful in hybrid and multi-cloud environments where physical separation isn’t practical and different cloud providers can be assigned their own virtual segments.  

Physical Segmentation  

Physical segmentation involves dividing the network into separate segments using dedicated hardware and infrastructure, such as different switches or routers. This method provides the highest level of isolation since each segment is physically disconnected from others, making it extremely difficult for threats to spread between segments. 

When to use physical segmentation:  

Physical segmentation is often used in larger networks with strict security requirements, such as those handling sensitive data or intellectual property. 

Perimeter-Based Segmentation  

Perimeter-based segmentation focuses on defining boundaries between trusted internal networks and untrusted external networks, typically via firewalls or ACLs.  

While this method traditionally focused on North-South traffic (in and out of the network), modern perimeter-based segmentation also considers East-West traffic (lateral movement) by controlling traffic flows between internal segments. However, as networks grow more complex, relying solely on perimeter defenses becomes less effective. 

The Most Common Network Segmentation Methods 

Within these broader categories, most organizations still rely on foundational approaches to network segmentation – 43% of security leaders say they use firewalls to segment their networks and 30% say they use VLANs.  

Notably, only 5% of organizations report that they’re currently microsegmenting their networks, even though it’s easier than ever to implement comprehensive, granular network segmentation.  

Network Segmentation Benefits: Security, Compliance, and Performance 

Network segmentation delivers benefits spanning:  

• Security: By dividing a network into smaller segments, network segmentation limits the scope of unauthorized access, reduces lateral movement, accelerates threat containment, and strengthens overall security posture.  
• Regulatory Compliance: Network segmentation aids in maintaining regulatory compliance by creating boundaries for sensitive data and implementing necessary security measures for each segment. By building a resilient, adaptive architecture, network segmentation also future-proofs compliance initiatives, making it easier to comply with regulatory changes.  
• Network Performance: Because network segmentation reduces congestion and optimizes traffic flows, it improves performance and enhances user experiences.  
• Troubleshooting and Maintenance: With network segmentation, administrators can isolate and address issues within specific segments without impacting the entire network.  

Let’s take a closer look at how network segmentation delivers benefits in each of these areas.  

Enhance Network Security  

Network segmentation strengthens security by blocking the lateral movement of malicious actors within the network. Since segments are proactively isolated, the larger network remains protected even if one segment is compromised. This prevents the infiltration of malware, ensuring that it cannot spread to critical systems and compromise sensitive data or intellectual property. 

Reduce the Attack Surface  

Network segmentation plays a pivotal role in minimizing the scope of a cyberattack. By dividing a network into smaller segments, each with its own dedicated resources and security controls, network segmentation shrinks the blast radius of an attack significantly.  

When an attacker gains unauthorized access to a segment, network segmentation ensures their activities remain isolated within that specific segment, preventing the attack from spreading to other segments or critical systems within the network. Limiting the scope of a cyberattack to one segment allows network administrators to more easily contain, investigate, and mitigate the incident. 

Protect Critical Assets and Devices  

Network segmentation stops attackers from reaching mission-critical parts of the network – even if they do not have advanced security measures of their own. For example, a hospital may deploy network segmentation to protect lifesaving medical devices from attacks. 

Since network segmentation also allows for tailored security measures and access control policies within each segment, unauthorized access to critical resources is mitigated even when a breach occurs within a different segment.  

Streamline Troubleshooting and Maintenance  

Network segmentation makes it easy for administrators to isolate specific areas of the network for troubleshooting and maintenance. Because issues can be localized to the specific segment where the problem is originating, network segmentation shrinks the scope of troubleshooting efforts. This targeted approach saves time and resources, allowing for faster resolution.  

Automating network segmentation further streamlines troubleshooting and maintenance processes. With tools that can automatically identify and classify new assets and data, network administrators can quickly adapt to changes within the network, cut out unnecessary manual effort, and limit the risk of human error.  

Optimize Network Performance  

Network segmentation reduces congestion and enables control over the flow of traffic. Tailored policies ensure that each segment is responsible for a specific set of tasks, preventing overcrowding and enabling smoother data transmission. 

By limiting the number of connected devices within each subnet, network administrators can tightly control competition for network resources to improve the network’s overall speed and efficiency, accelerating data packets and leading to faster response times.  

Additionally, network segmentation allows for better traffic control. By separating different types of traffic, such as internal and external, organizations can prioritize critical data flows and allocate resources accordingly. This level of control enables seamless communication and minimizes the risk of bottlenecks or slowdowns. 

Simplify Cybersecurity Compliance 

Cybersecurity compliance refers to an organization's adherence to industry-specific regulations and standards related to network and security practices. Implementing network segmentation helps organizations achieve and maintain regulatory and cyber insurance compliance by ensuring proper management of vulnerabilities, permissions, and updates. 

Segmentation plays a crucial role in compliance as it allows organizations to segregate sensitive data and resources into distinct segments, each with its own set of security controls and access policies. By isolating data based on regulatory requirements, organizations can easily identify and manage the systems that fall within the scope of compliance initiatives, reducing the complexity of compliance efforts and enabling efficient monitoring and auditing procedures. 

Meanwhile, network segmentation ensures that only necessary components are subject to compliance requirements, reducing the costs associated with implementing and maintaining compliance measures. Instead of applying costly and time-consuming controls to the entire network, organizations can focus their resources on securing and monitoring only the segments that handle regulated data or perform critical functions.  

How Network Segmentation Works: Key Components and Capabilities 

To keep subnetworks securely isolated, traditional network segmentation relies on a variety of key controls working in chorus:  

Internal Firewalls and ACLs  

Internal firewalls and access control lists (ACLs) are often implemented within the segmented network to enforce the isolation of subnetworks. Internal firewalls enforce policies between segments, controlling which traffic can pass and preventing unauthorized lateral movement between segments. ACLs work alongside internal firewalls by defining the traffic flows allowed between segments and filtering network traffic based on predetermined rules.  

How Do ACLs  Work in Network Segmentation?  

ACLs work by defining rules that determine which traffic is allowed or denied between segments. These rules can be based on criteria like source and destination IP addresses, port numbers, protocols, or specific user identities.  

By enforcing these rules, ACLs ensure that only authorized traffic is allowed to pass between segments, while malicious or unauthorized traffic is blocked. 

Incorporating internal firewalls and ACLs into a segmentation strategy helps further compartmentalize the network, making it more challenging for attackers to navigate.  

VLANs and Subnets 

Two of the most common approaches to logical segmentation are VLANs and subnets. VLANs work by:  

• Creating multiple virtual networks within a single physical network infrastructure  
• Assigning specific ports, switches, or users to different VLANs 
• Isolating traffic between VLANs and controlling access to resources 

This simplifies network management and ensures that devices within the same VLAN can communicate while remaining isolated from other VLANs. 

Organizations can also create distinct segments with their own subnet address ranges. This allows for: 

• Efficient IP address management 
• The ability to enforce access control and security policies at the subnet level 
• Automated provisioning and configuration processes through network addressing schemes, reducing human error and streamlining network operations 

VLANs vs. Modern Network Segmentation 

VLANs are a foundational steppingstone in network segmentation – they offer a straightforward and cost-effective way to logically separate networks without requiring additional physical infrastructure. However, VLANs aren’t equipped to protect against sophisticated cyber threats – for that, organizations need a next-gen segmentation approach, like microsegmentation.  

As Crystal Chadwick, a Customer Engineer at Zero Networks, points out, “A VLAN is a very simple but ineffective way to separate networks.” This simplicity often leads to significant security gaps in modern, dynamic environments.   

Traffic Flow Isolation 

By categorizing and isolating traffic flows, organizations can enhance both network performance and security. Network administrators assign specific segments or subnetworks to different types of traffic, such as user, management, or data traffic – this segregation prevents potential threats from spreading across the network.  

For example, if a user device is compromised and becomes a source of malicious traffic, traffic flow isolation ensures that this traffic is contained within its designated segment and does not impact other parts of the network. 

Network Segmentation and Zero Trust: Secure by Default 

Nine out of ten IT and security leaders agree Zero Trust is key to improving their overall security posture, and network segmentation is a critical enabler for accelerating these journeys.  

How Network Segmentation Advances Zero Trust Security  

Because network segmentation divides a network into smaller, secure subnetworks, each with its own access controls and policies, it adheres to the Zero Trust guidance to treat every request as potentially malicious.  

Chadwick explains, “Segmentation helps implement Zero Trust by limiting what’s accessible to any user or device at any time. Even if an attacker gains entry, they’re effectively trapped within that segment and cannot move laterally to access more sensitive systems.” 

Network Segmentation in Zero Trust Frameworks 

Both the NSA and CISA frameworks highlight segmentation as essential to maturing key Zero Trust pillars: 

• The NSA requires network segmentation in its blueprint for the Network & Environment pillar, instructing organizations to isolate systems and apply dynamic, risk-based access policies.  
• CISA’s Zero Trust Maturity Model highlights network segmentation as key for mitigating unauthorized access 

With all of this in mind, it’s easy to see why more than 90% of organizations are currently using or planning to use network segmentation as part of their Zero Trust strategy. 

Network Segmentation Challenges

Historically, implementing and maintaining network segmentation tools has been costly and difficult. Traditional approaches like internal firewalls, ACLs, and VLANs have become outdated and cumbersome.  

While any level of network segmentation is better than nothing, these legacy segmentation strategies bring disadvantages like:  

• Significant manual work, leading to misconfigurations and vulnerabilities 
• Lack of granularity and visibility 
• Complex maintenance and scalability  
• Inadequate protection against sophisticated threats 

What’s more, today’s sprawling, complex networks render these traditional approaches largely ineffective. In hybrid networks, the perimeter is blurry and therefore impossible to effectively secure with a traditional approach. And, since these old-school segmentation methods are typically based on trust (meaning whatever is inside the network or network region is trusted and everything outside is not), attackers face little resistance if they are able to breach the perimeter. 

For example, if an organization segments its network by function and an attacker manages to breach their finance department, the attack – while isolated to one segment – would still be catastrophic to the organization. The attacker would also likely reach at least one machine it could use to move laterally and then repeat the process to reach most or all of the network.  

In other words, basic network segmentation is a step in the right direction, but it doesn’t go far enough to stop attackers in their tracks. To move past the shortcomings of legacy segmentation approaches, organizations must embrace microsegmentation.  

Network Segmentation vs. Microsegmentation

Unlike traditional network segmentation – which involves dividing a large network into smaller subnetworks, or segments – microsegmentation is a much more granular and robust process of isolating all clients, workloads, applications, virtual machines, and operating systems into isolated segments with unique security perimeters. 

Microsegmentation has long been considered the most effective way to prevent lateral movement, protect against ransomware, and enable real-time threat containment as it reduces the attack surface to virtually nothing. But legacy microsegmentation solutions feature many of the same challenges as traditional segmentation approaches – they’re complex, labor-intensive, and time-consuming. Fortunately, modern microsegmentation capabilities like automation and network layer MFA remove those traditional barriers.  

Next-Gen Network Segmentation: Granular, Automated Protection 

Zero Networks’ automated microsegmentation solution adapts to your environment, keeping only the necessary connections between machines open. By leveraging network-layer MFA, Zero ensures normal, uninterrupted usage for non-admin users while only granting temporary admin access after just-in-time MFA verification.  

Automated, agentless microsegmentation allows security leaders to:  

• Isolate everything (down to the individual machine) with a single click  
• Stop lateral movement without interrupting normal network traffic 
• Scale security alongside network changes – no need for agents or manual operation 
• Streamline operations and cut out the cost of NACs, internal firewalls, IPS, and manual, ACL-based microsegmentation 
• Stay compliant with cyber insurance policies and regulations 

Zero brings powerful, precise microsegmentation within reach in days – not years – no matter the size of your team. Take a self-guided product tour to find out how Zero Networks is making next-gen network segmentation effortless.