Flat networks create paradise for attackers. Compromising a single system grants access to every other system on the network. Network segmentation limits this access, dramatically reducing breach impact.
The concept sounds simple: divide networks into smaller segments with controlled communication between them. Implementation proves far more complex. Organisations struggle with balancing security against operational requirements and complexity.
VLANs provide basic segmentation by separating broadcast domains. Traffic between VLANs must traverse a router or layer 3 switch, where filtering rules can be applied. However, VLAN hopping attacks can bypass this protection if switches aren’t properly configured.
Micro-segmentation takes network segmentation to its logical conclusion. Rather than segmenting by department or location, micro-segmentation controls traffic between individual workloads. This approach requires software-defined networking or next-generation firewalls that can enforce granular policies. Professional internal network penetration testing examines whether your segmentation controls actually prevent lateral movement.
Zero-trust architecture relies heavily on network segmentation. By treating the network as hostile, zero trust eliminates implicit trust based on network location. Traffic gets inspected and authorised regardless of source or destination network.
William Fieldhouse, Director of Aardwolf Security Ltd, explains: “Network segmentation represents one of the most effective security controls available. When we conduct internal network penetration testing, properly implemented segmentation stops lateral movement cold. Poor segmentation allows us to compromise the entire network from a single initial foothold.”
DMZ (demilitarised zone) networks isolate internet-facing services from internal networks. Web servers, email gateways, and other externally accessible systems sit in the DMZ. Strict firewall rules allow only necessary traffic between the DMZ and internal networks.
Jump servers or bastion hosts control access to sensitive network segments. Administrators must first connect to the jump server, which logs all activity, before accessing production systems. This approach provides centralised access control and comprehensive audit trails.
Application-layer segmentation controls traffic based on application protocols and behaviour rather than just IP addresses and ports. Next-generation firewalls inspect application traffic, identifying specific applications and enforcing granular policies based on application identity.
Database network segmentation isolates data tier from application and web tiers. Database servers should never be directly accessible from user networks. Applications communicate with databases through well-defined APIs over tightly controlled network paths.
Guest network segmentation prevents visitor devices from accessing internal resources. Compromised guest laptops or malicious visitors shouldn’t be able to probe internal systems. Completely isolated guest networks with internet-only access protect organisations while maintaining hospitality. Working with the best penetration testing company ensures a comprehensive evaluation of your segmentation strategy and implementation.
Industrial control system segmentation separates operational technology from IT networks. ICS environments have unique security requirements and often run ancient, unpatched systems. Air gaps or highly restricted network connections prevent IT security incidents from disrupting industrial processes.
