1.What is network segmentation?
Network segmentation consists of dividing a computer network into multiple distinct sub-networks, called segments.
Each segment groups systems with similar functions and applies specific communication rules between them.
The main objectives are to:
– limit the spread of attacks
– improve network visibility
– strengthen access control
2.Why is network segmentation essential?
In a non-segmented network, devices can often communicate freely with each other.
This means that an attacker who compromises a single machine may gain access to the entire information system.
Network segmentation helps to:
– contain attacks
– protect critical resources
– reduce the attack surface
– enforce the principle of least privilege
3.How does network segmentation work?
Network segmentation relies on several technical mechanisms:
– VLANs (Virtual LANs) to logically separate traffic
– firewalls and ACLs (Access Control Lists) to control communications
– secure inter-segment routing
– monitoring traffic between security zones
Each segment has its own access rules, preventing standard user workstations from directly accessing sensitive servers.
4.Main types of segmentation
Physical segmentation
– uses separate hardware (switches, routers, dedicated cabling)
– very secure
– costly and inflexible
Logical segmentation
– based on VLANs and software-based rules
– the most common approach in enterprise environments
Micro-segmentation
– very fine-grained segmentation (per application or per host)
– widely used in cloud and modern data center environments
5.Real-world examples and incidents
Target breach (2013 – United States)
Retailer Target suffered a massive payment card data breach affecting over 40 million customers.
Root causes:
– compromise of a third-party vendor
– lack of proper network segmentation
– lateral movement to payment systems
Strict segmentation between vendor networks and critical systems would have significantly limited the attack.
WannaCry (2017)
The WannaCry ransomware spread rapidly across thousands of organizations and hospitals.
Key factors:
– flat internal networks
– exploitation of vulnerable SMB protocol
– no barriers between user workstations and servers
Well-segmented organizations were able to contain the attack to only a few machines.
Hospital environments
Historically, many hospitals used a single network for:
– medical devices
– administrative workstations
– guest Wi-Fi access
Result:
– a simple workstation infection could impact critical medical equipment
Network segmentation has now become essential in healthcare environments.
6.Benefits of network segmentation
– limitation of lateral movement by attackers
– improved protection of sensitive data
– precise control of network flows
– compliance with standards (ISO 27001, PCI-DSS, NIS2)
– improved incident detection
7.Limitations and constraints
– implementation complexity
– risk of misconfiguration
– need for clear documentation
– increased network management effort
Poorly designed segmentation can introduce vulnerabilities or cause service disruptions.
8.Conclusion
Network segmentation is one of the most effective ways to reduce the impact of cyberattacks.
Major incidents such as Target and WannaCry clearly show that flat networks represent a critical risk.
When properly designed, segmentation helps contain attacks, protect sensitive assets, and strengthen the overall resilience of the information system.
It should be viewed not as an option, but as a modern security standard.
(NIST – Special Publication 800-53: Security and Privacy Controls)
(NIST – SP 800-207: Zero Trust Architecture)
(ENISA – Network Segmentation Practices)
(SANS Institute – Network Segmentation and Defense-in-Depth)
(Verizon – Data Breach Investigations Report (DBIR))
(Mandiant – Global Threat Intelligence Reports)
(PCI Security Standards Council – Network Segmentation Guidance)
(Public breach analysis – Target Data Breach (2013))
(Microsoft Security Response Center – WannaCry Technical Analysis)