# Network Segmentation: Limiting Breach Impact
Flat networks simplify operations. Any device can reach any other device. Troubleshooting avoids firewall rules. Applications deploy without network requests. This simplicity enables attackers too.
Once inside a flat network, attackers move laterally without impediment. Compromise one workstation, access every server. Ransomware spreads unchecked. Data exfiltration proceeds unobstructed.
Network segmentation limits blast radius. Boundaries contain compromise. Attackers must breach each segment individually. Defence gains time and detection opportunities.
## Segmentation Strategies
Multiple approaches implement segmentation.
**VLAN segmentation** separates at layer 2. Different VLANs for different purposes. Routing between VLANs enables controlled connectivity. Simple to implement on existing infrastructure.
**Firewall segmentation** controls layer 3 and above. Rules permit specific traffic between segments. Stateful inspection validates connection patterns. More granular than VLANs alone.
**Microsegmentation** extends to individual workloads. Software-defined policies control VM to VM traffic. East-west traffic filtering within segments. Zero trust principles applied throughout.
## Segmentation Design
Effective segmentation requires thoughtful design.
**Identify critical assets** first. What data matters most? Which systems enable business operations? These require strongest protection.
**Define trust zones** based on sensitivity and function. Production separate from development. Sensitive data isolated from general access. External-facing systems in DMZ.
**Map communication requirements** before implementing. What needs to talk to what? Document legitimate traffic flows. Segmentation should enable, not just restrict.
**Start coarse, refine over time.** Initial segmentation separates major zones. Monitoring reveals actual traffic patterns. Progressive refinement increases granularity.
## Implementation Considerations
Practical segmentation involves more than firewall rules.
**Application awareness** matters. Modern applications span tiers. Segmentation must accommodate legitimate application traffic. Service discovery and communication patterns must be understood.
**Operations impact** requires attention. Troubleshooting across segments is harder. Management access must be preserved. Change processes need updating.
**Monitoring** becomes more important. Segmentation creates boundaries worth watching. Traffic crossing segments deserves scrutiny. Alerts for unexpected cross-segment communication.
If your organisation needs help designing network segmentation or implementing zero trust architecture, contact us through our contact page.
## Segmentation as a Ransomware Control
Segmentation limits lateral movement. In practice:
- separate user networks from servers,
- isolate management interfaces,
- and restrict east-west traffic between critical tiers.
## Start With Visibility
Before you block traffic, measure it:
- flow logs,
- firewall logs,
- and dependency mapping.
Then implement least privilege rules with staged rollouts.