Modern organizations depend on connected systems to support business operations. Employees access file servers, cloud applications, databases, and internal services throughout the day. While connectivity is essential for productivity, it also creates opportunities for attackers to move through a network after compromising a single device. One of the most effective ways to reduce this risk is network segmentation.
Network segmentation divides a network into smaller, controlled sections, limiting communication between systems that do not need to interact. For Security Operations Center (SOC) analysts, understanding network segmentation is important because it reduces the attack surface, limits lateral movement, and provides valuable context during security investigations. Both the MITRE ATT&CK framework and the NIST Cybersecurity Framework (CSF) recognize the importance of restricting access and protecting critical systems.
What Is Network Segmentation?
Network segmentation is the practice of separating systems into different network segments based on their function or security requirements.
For example, an organization may place:
- Employee workstations on one network.
- Domain controllers on another.
- Database servers in a protected segment.
- Public-facing web servers in a demilitarized zone (DMZ).
Firewall rules and access control policies determine which systems are allowed to communicate with one another.
If an attacker compromises an employee workstation, proper segmentation can prevent direct access to critical servers, significantly reducing the scope of a potential incident.
MITRE ATT&CK and Lateral Movement
Many techniques in the MITRE ATT&CK framework involve expanding access after an initial compromise.
For example, T1021 – Remote Services describes how attackers use protocols such as Remote Desktop Protocol (RDP), Server Message Block (SMB), or Secure Shell (SSH) to move laterally between systems.
Without network segmentation, attackers may have unrestricted access to numerous systems once they compromise a single endpoint.
With segmentation in place, unauthorized connections are more likely to fail or generate security alerts. This not only slows the attacker but also creates valuable detection opportunities for SOC analysts.
Instead of investigating activity across the entire network, analysts can focus on unusual communication between protected network segments.
NIST Recommendations
The NIST Cybersecurity Framework emphasizes protecting critical assets through access control and network security.
Organizations should identify systems containing sensitive information and restrict communication to only those users and services that require access. Network segmentation supports the Principle of Least Privilege by limiting access at the network level rather than relying solely on user permissions.
NIST also recommends continuously monitoring network traffic to identify unauthorized communication between systems. Unexpected connections across network segments may indicate attempted lateral movement or policy violations.
Investigation Tips
When reviewing network activity, SOC analysts should consider several questions:
- Is communication between these two systems expected?
- Has this endpoint previously accessed this server?
- Which user initiated the connection?
- Does the connection align with normal business operations?
- Are there related authentication or process creation events?
Correlating firewall logs, Windows authentication events, EDR telemetry, and DNS records provides valuable context and helps determine whether unusual network communication represents malicious activity.
Conclusion
Network segmentation is one of the most effective security controls for reducing the impact of cyberattacks. By limiting communication between systems, organizations reduce the opportunities available to attackers while improving visibility into suspicious network activity.
Combined with the behavioral guidance provided by the MITRE ATT&CK framework and the access control recommendations of the NIST Cybersecurity Framework, network segmentation strengthens enterprise security and supports faster, more effective incident response. For SOC analysts, understanding how systems are separated within the network is essential for detecting lateral movement and protecting critical business assets.