Network Segmentation

Network segmentation is a foundational security architecture practice that reduces the attack surface by creating boundaries between different parts of an organization's network. Instead of operating a flat network where any device can communicate with any other device, segmentation creates distinct zones — for example, separating production systems from development environments, isolating payment processing infrastructure, or creating dedicated segments for sensitive data stores. If an attacker compromises one segment, the segmentation boundaries prevent easy lateral movement to other parts of the network.

From a compliance perspective, network segmentation is frequently cited as both an expected control and a scope-reduction mechanism. In SOC 2 audits, demonstrating effective network segmentation shows that security controls are in place to protect system boundaries. ISO 27001 Annex A controls on network security (A.8.20-A.8.22) directly address network segmentation, filtering, and segregation of network services. For PCI DSS compliance specifically, segmentation can reduce the scope of the assessment by isolating the cardholder data environment. NIS2 requires essential entities to implement measures for network security, which naturally includes segmentation strategies.

Modern network segmentation has evolved beyond traditional VLAN-based approaches. Micro-segmentation applies granular policies at the workload or application level, often using software-defined networking. Cloud environments require segmentation through virtual private clouds (VPCs), security groups, and network policies. Container orchestration platforms like Kubernetes introduce their own network policy mechanisms. Effective segmentation requires maintaining an up-to-date network architecture diagram, defining clear communication policies between segments, monitoring cross-segment traffic for anomalies, and regularly testing that segmentation rules are functioning as intended.