Network Segmentation Series: What is It?

February 15, 2021
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2 min read

This is the first in a series of three blog posts about network segmentation. 

Many businesses are looking to augment their defenses by changing their approach to network security. Take the heightened awareness around building zero trust networks, for instance. Embracing the shift to zero trust will require users to address the threat of lateral movement. One of the ways they can do this is by segmenting the network according to their security needs. But this raises an important question: how does one segment a network well?

To answer that question, I’ll look at the principle of network segmentation over the span of three blog posts. Let’s start off slow. How do you define network segmentation? What benefits can you reap by segmenting the network?

What is Network Segmentation?

Network segmentation is the process of breaking a network into smaller networks. Firewalls, for example, can prevent traffic that began in one part of the network from reaching another segment. Admins could also choose to enforce this based upon the type, source or destination of specific traffic.

In whatever way it’s put in place, network segmentation aims to respond to the weaknesses of a ‘flat’ network model, where everything is trusted. The danger with such a network model is that malicious actors could gain access to sensitive data by capitalizing on a single network intrusion and moving sideways. Segmentation addresses that threat by limiting access to sensitive systems, hosts and data.

What Are the Benefits of Network Segmentation?

Network segmentation can help prevent, spot and respond to potential threats. One main benefit is in the way it brings improved access controls for both internal and external network defenses. It can also prevent external actors from finding a foothold in the network, as well as blocking attackers who are already in the network from moving laterally. That’s why network segmentation is so important when splitting what’s trusted from what’s untrusted in a zero trust network.

Network segmentation can also help detect potential intrusions with custom network monitoring tools. If a security expert watching out for a critical section spots anything weird, they only have to check one segment instead of an entire flat network. This could limit the scope of a ransomware attack, for instance. It also makes it safer to deploy Internet of things (IoT) devices that might lack security by design in a way that doesn’t put the rest of the network at risk.

The benefits aren’t just in the security realm, either. When done correctly, admins can shape traffic in such a way that reduces network congestion and thereby improve performance. They can also use network segments to partition the attack surface and/or their existing risks in a way that makes it easier for them to fulfill their compliance goals. For instance, medical organizations could separate protected health information on one segment and concentrate their compliance efforts there instead of throughout the entire network.

Not Always a Smooth Ride

Clearly, organizations can reap many benefits from network segmentation. But doing so isn’t always easy. I’ll discuss some challenges that you could face along the way in the next post in this series.

David Bisson
Contributing Editor

David Bisson is an infosec news junkie and security journalist. He works as Contributing Editor for Graham Cluley Security News and Associate Editor for Trip...
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