Key Concept
Network segmentation divides your network into smaller, isolated segments to limit the spread of security breaches and improve overall network security and performance.
Introduction
Network segmentation is a critical security strategy that involves dividing your network infrastructure into smaller, more manageable segments. For small and medium enterprises (SMEs), implementing effective network segmentation can dramatically improve security posture whilst maintaining operational efficiency.
Rather than having all devices on a single "flat" network where a compromise of one system can potentially affect all others, segmentation creates barriers that limit the lateral movement of threats. This approach is particularly important for Cyber Essentials compliance, where boundary firewalls and access controls are key requirements.
Key Points
Network Segmentation Benefits
- Limits lateral movement of security threats across the network
- Improves network performance by reducing broadcast domains
- Enables granular access control and monitoring
- Facilitates compliance with security frameworks
- Isolates critical systems from general network traffic
Understanding VLANs
Virtual Local Area Networks (VLANs) are the most common method of implementing network segmentation in SME environments. VLANs allow you to logically separate network traffic without requiring separate physical infrastructure for each segment.
A typical SME VLAN setup might include: a management VLAN for network equipment administration, a user VLAN for employee devices, a server VLAN for critical business systems, a guest VLAN for visitor access, and an IoT VLAN for smart devices and sensors.
Implementing Guest Wi-Fi
Guest Wi-Fi networks should be completely isolated from your business network. This prevents visitors from accessing internal resources whilst still providing internet connectivity. Configure your guest network on a separate VLAN with strict firewall rules that only allow internet access.
Consider implementing time-based access controls, bandwidth limitations, and regular password rotation for guest networks. Some organisations also implement captive portals that require registration or acceptance of terms and conditions before granting access.
Practical Implementation Steps
Start by documenting your current network topology and identifying different types of devices and their security requirements. Plan your VLAN structure based on device types, security levels, and access requirements. Most SMEs can implement effective segmentation with 4-6 VLANs.
Configure your managed switches to support VLANs and assign appropriate ports to each VLAN. Update your firewall rules to control inter-VLAN communication, applying the principle of least privilege. Document your segmentation strategy and ensure your team understands the new network structure.
Cyber Essentials and Network Segmentation
Cyber Essentials requires organisations to implement boundary firewalls and control access between internal and external networks. Network segmentation supports these requirements by creating additional internal boundaries that can be monitored and controlled.
The segmentation also helps with the user access control requirements of Cyber Essentials, as different VLANs can enforce different access policies. This approach demonstrates a mature understanding of network security principles that assessors look for during certification.
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