10 Network Segmentation Best Practices for Robust Cybersecurity in 2024

Network segmentation involves dividing a network into isolated segments based on sensitivity and business needs. By implementing segmentation, an organization can limit the potential impact of network intrusions and support a zero trust architecture. In a segmented network, traffic crossing segment boundaries must pass through a firewall, which can implement access controls and look for signs of a potential intrusion.

Foundational Principles for Effective Network Segmentation

Key principles for an effective network segmentation strategy include:

• Least Privilege: The principle of least privilege means that users, devices, and applications should only have the access necessary for their roles. Network segmentation should be designed to support this principle.
• Business Alignment: Define network segment boundaries based on business needs and system roles. This minimizes the operational impact on legitimate network communications while impeding an attacker’s ability to move through the network.
• Secure Segment Boundaries: Network segmentation should isolate network segments and prevent unauthorized traffic from crossing boundaries. To accomplish this, segment boundaries should be secured using a next-generation firewall (NGFW) and strong access controls.

Top 10 Network Segmentation Best Practices

#1. Identify and Classify Critical Assets

Segment the corporate network based on the criticality and roles of assets. To accomplish this, an organization first needs to generate an inventory of the assets that need to be secured.

A network segmentation policy will define the architecture of the entire corporate network. However, focusing on high-value and high-risk assets first will help to ensure that they are properly protected and that the network segmentation policy offers maximum return on investment. 

#2. Mapping Business Flows

Understanding how data moves throught the organization is essential to define segment boundaries and identify critical points that need protection. Take the following steps to map business flows:

• Identify Key Processes: Understand and document the key business processes and how data flows between different systems and departments.
• Analyze Data Movement: Determine how data moves across the network, including interactions between applications, databases, and users.
• Prioritize Segmentation: Use insights from business flow mapping to prioritize network segments that align with critical business functions and data flows.
• Context: Mapping business flows helps to ensure that network segmentation supports business operations and enhances security by focusing on the most critical data paths.

#3. Define Clear Segmentation Policies

Once the infrastructure is understood, define clear network segmentation policies. Ideally, these should be based on the organization’s business needs and the sensitivity of the assets within a segment. For example, an application and a database that it frequently accesses might be within the same segment, but a critical system within the same department might be isolated in its own segment.

When designing and implementing network segmentation policies, it is important to document these policies as well thoroughly. This helps to ensure consistency, auditability, and future security by laying out the structure of the segment and the security rationale behind it.

#4. Leverage Virtual Segmentation Techniques

Software-based solutions offer a flexible and cost-effective approach to network segmentation compared to physical implementations. Implementing network segmentation in code allows trust boundaries to be updated as needed when the corporate network evolves.

Organizations have multiple options for implementing virtual network segmentation, such as the use of virtual LANs (VLANs) and software-defined networking (SDN). Modern solutions also offer the ability to implement micro-segmentation, providing more granular access control and security enforcement for traffic moving laterally within the organization.

#5. Implement Strong Access Controls

Network segmentation helps organizations manage access more effectively within the corporate network. Access controls should implement the principle of least privilege, limiting access to the bare minimum required for a particular role.

Role-based access control (RBAC) offers an effective and scalable means of accomplishing this by granting permissions to a particular role, which is then assigned to a user or other entity. By mapping permissions to roles, organizations can assign the role to all applicable users, and they can change permissions once and have the updates applied to everyone with that role.

Access controls should also be supported with security best practices, such as the use of multi-factor authentication (MFA). Access permissions should also be regularly reviewed and updated to ensure that they meet business needs and continue to implement least privilege.

#6. Deploy Strategic Firewalls and Gateways

Segmentation divides the network into isolated zones. This is commonly implemented using internal firewalls that inspect network traffic before allowing it to cross segment boundaries.

When deploying these firewalls, it’s important to ensure that firewall rules are configured appropriately. They should implement corporate security policies and enforce access controls but should also minimize their impact on legitimate business operations.

#7. Restrict Third-Party Access

Vendors and partners may require access to corporate systems. However, this access should be implemented using the principle of least privilege and taken into account in an organization’s network segmentation policy.

External parties should have access to only necessary systems, which will ideally be located within their own network segment. Third-party access should be provided via separate portals and jump hosts and be closely monitored for potentially anomalous or malicious activities.

#8. Monitor and Audit Continuously

Continuous monitoring is essential to manage network security and maximize the effectiveness of network segmentation. Organizations should implement automated monitoring and promptly investigate usual or suspicious activity. Based on these investigations, it may be necessary to update policies to further restrict access or create exceptions for legitimate traffic.

It is also wise to perform regular in-depth audits of the organization’s network segmentation policy. This helps to ensure that segmentation controls are effective and that segment boundaries are properly defined. For example, the deployment of a new application on an existing server may change its sensitivity level, prompting a move to a new network segment.

#9. Prioritize Governance and Documentation

Governance and documentation are essential for the success of a network segmentation policy. All aspects of the architecture, policies, and procedures should be clearly documented to support future incident investigations, network updates, and security audits.

It’s also important to keep in mind that segmentation can have impacts on the entire organization. When developing and implementing segmentation policies, stakeholders from affected departments should be involved and solicited for feedback. Additionally, the organization should conduct training to ensure that affected stakeholders understand how the segmented architecture works and how to monitor, operate, and secure it.

#10. Plan for Scalability and Adapt to Change

As corporate networks grow and evolve, so do their network segmentation needs. When selecting tools and technologies, it’s important to choose ones that are capable of growing and adapting with the business. This is a major advantage of logical vs. physical network segmentation.

The organization should also work to support the growth and evolution of its network segmentation strategy. Performing regular assessments of the strategy can help to identify potential changes that may be needed as the environment evolves. Additionally, the network and security teams should leverage automated management tools whenever possible to alleviate the burden of required updates.

Overcoming Obstacles to Effective Network Segmentation

Implementing network segmentation can have significant benefits for network security and performance. However, organizations may be wary of doing so due to potential challenges. 

Some common obstacles that organizations face include:

• Complexity and Cost: Network segmentation involves rearchitecting the corporate network to build in additional monitoring and security. By using virtual solutions such as vLANs and SDN, an organization can perform segmentation at the logical level without the need for costly and complex changes to physical infrastructure.
• Buy-In and Support: Getting organizational buy-in and support may be difficult if the benefits of segmentation are not communicated to key stakeholders. Highlighting the potential security, compliance, and performance benefits of segmentation can help to demonstrate the value to the business.
• Avoiding Business Disruption: Implementing network segmentation can negatively impact corporate productivity if solutions and access controls are not properly configured. Thorough testing and a phased rollout can help to minimize potential business disruptions during the implementation process.

 Conclusion

Network segmentation can help to manage an organization’s exposure to security risks and improve visibility and access management within the corporate network. When implementing network segmentation, it’s important to consider security and business requirements and select solutions that can grow and evolve with the business.
Zero trust network access (ZTNA) is an effective and scalable means of implementing network segmentation across the corporate WAN as part of a corporate zero trust strategy. Learn more about implementing segmentation and zero trust with ZTNA and secure access service edge (SASE).