How to segment a network for better security

· Category: Cybersecurity

Short answer

Network segmentation divides a network into smaller zones, each with its own security controls. It prevents attackers from moving freely after an initial compromise.

Steps

  1. Classify assets: Group systems by sensitivity and function, such as production, development, guest, and management.

  2. Create VLANs and subnets: Assign each group to a dedicated VLAN with a unique IP subnet.

  3. Deploy internal firewalls: Place stateful inspection or NGFWs between segments to enforce zone-to-zone policies.

  4. Define access rules: Allow only necessary protocols and ports between zones. Default to deny.

  5. Implement microsegmentation: In virtualized environments, apply policies down to the individual workload level.

  6. Monitor east-west traffic: Log and alert on unusual lateral movement between segments.

Tips

  • Keep management interfaces on a separate segment inaccessible from user VLANs.
  • Use jump hosts for administrative access between segments.
  • Review segment boundaries during architecture changes.

Common issues

  • Overly permissive rules between segments defeating the purpose.
  • Forgotten legacy connections creating backdoors.
  • Lack of monitoring making lateral movement invisible.