Taking Advantage of Network Segmentation in 2019


Security is and will always be top of mind within organizations as they plan out the year ahead. One method of defense that always deserves attention is network segmentation.

In the event of a cyberattack, segmented networks will confine the attack to a specific zone – and by doing so, contain its impact by preventing attackers from exploiting their initial access to move deeper into the network. By segmenting your network and applying strong access controls for each zone, you isolate any attack and prevent damage before it can start.

But today, in 2019, enterprise networks are no longer just networks. They are a patchwork of traditional networks, software-defined-networks, cloud services and microservices. Segmenting this hybrid conglomerate requires an updated approach.

In this article, I will review exactly how your organization can get started with network segmentation – including some potential issues to plan for and successfully avoid.

Getting Started

Organizations seeking a starting point typically find that designating rudimentary network zones is the most successful approach. Start with simple zones to begin segmentation, even for today’s more complex hybrid networks. Initial zones typically include Internal, External, Internet, and DMZ. Further refinements to segments and access policies can be made to these initial zones, ultimately resulting in an acceptable policy.

Solidify Your Security Policy

Organizations need a standard policy for allowable ports and protocols between zones. This needs to be fully documented and in a format that can be quickly accessed and reviewed – not something unofficial that’s stuck in the head of your IT security manager. Once security policy is transcribed and centralized in a single place, each modification to access policies can be made consistently and confidently.

As your segmentation initiative continues, take the opportunity to consider segmenting the network even further using user identity and application controls.

Restrict Egress

Most likely, your network is already infected and even if it isn’t, it’s a good practice to assume so. Completely preventing malware in your network is practically impossible. But luckily there's another mitigation that is easier. If you limit egress (outbound) connectivity to only what is needed, you can prevent malware from calling back home and from uploading stolen data.

Traditional Networks, the Cloud, and Beyond

As your network expands into the cloud you may need to partner with application teams. If your organization is moving to the cloud in a “lift and shift” approach, your cloud networks are probably considered an extension of your on-premise network and the traditional segmentation architecture will be applied. Organizations that are already doing “cloud native” operations (characterized by DevOps and CI/CD processes) take a different approach. They architect their cloud around applications rather than networks. In this case, the cloud will be owned by the relevant application team and, in the event of a security incident, you will need to work closely with them to contain the breach.

This exercise often results in two or more teams becoming united around a unified goal – while also providing an opportunity to improve the network’s connectivity and security. When you identify parts of the network you are responsible for segmenting, you will also want to include any anticipated networks that may be adopted or merged with your existing network. Understanding that these changes will introduce new security concerns and obstacles, you can better plan for the overall impact on your network segmentation strategy.

Make It Manageable

Parallel to ongoing changes in networking platforms are changes to network policy. This year, your organization may undertake a cloud-first initiative, launch new businesses, or open new locations across the globe – and you need to be ready for it.

Regardless of what changes in your network, there needs to be consistency over managing and tracking these changes. Identifying tools that have previously been configured on your network or are currently used to manage your network makes managing your segmentation process achievable from the start. If you identify multiple existing solutions, consider whether you can integrate them to create a central console for designing, implementing and managing ongoing segmentation.

Implement In Phases

Once you’ve reached this point in the segmentation process, you should know which resources are available and who can contribute to segmentation design and implementation. Armed with this knowledge, you should now set priorities.

First and foremost, assess the network at a high-level and consider what zones you will want to appoint (regardless of how rudimentary it seems). Even segmenting the network in half will provide you with greater management over connectivity, increase visibility over access and identify risks associated with existing access rules that you may have previously missed.

Starting with the initial four zones from above, you can identify further connectivity restrictions and prioritize which of the zones needs to be further segmented (e.g., sensitive data, cyber assets, etc.).

If you are required to comply with specific industry regulations, start by designating a sensitive data zone (for example, a zone for PCI DSS systems and data). You can begin with compliance in mind and then take a step back to approach the broader network. This approach will help you identify connectivity improvements, reduce access permissions, and complicate potential attacks on sensitive data.


When you start applying security, you apply it at the macro-level: zones, subnets, vlans, etc. As you make progress in your security journey, you can consider the micro as well. Modern architectures such as SDN, cloud platforms and Kubernetes microservices provide flexible methods to develop individual access control for applications in a security-first mentality (which is commonly referred to as micro-segmentation). Restricting connectivity per application gives you greater control with more specific whitelists and easier identification of abnormal behavior. To do this effectively you will need to involve application owners.

Don’t Do Too Much, Too Soon

Remember to segment in a gradual, deliberate progression as implementing such detailed control in your network can become unmanageable due to the sheer volume of segments.

When implementing network segmentation, it very important to avoid over-segmenting, as this may result in a loss of manageability due to increased complexity.  While segmentation improves overall compliance and security, organizations should segment incrementally in order to maintain manageability and avoid overcomplicating the network.  

Taking on too much, too soon – or moving to micro- or nano- segmentation from the beginning – can create an “analysis paralysis” situation, where the team is quickly overwhelmed and the promise of network segmentation is lost.

An example of doing too much could be assigning a security zone for every application in a 500-application environment. If every zone is individually customized, the sheer volume of network rules can overwhelm an organization, leaving your organization less secure.

Take Action

As anyone who’s worked a day in security knows, automated solutions can send an overwhelming number of alerts. Network Security Policy Management (NSPM) solutions can alleviate this alert fatigue. Violations to security policy can be reviewed to determine if they are allowable exceptions to the policy or require changes in order to comply. Beyond compliance with policy, NSPM solutions can assess whether access violations followed approved exception procedures or not.

Security professionals are often targeted by attackers. NSPM solutions can also be used to determine if network violations are the result of attackers using compromised credentials to grant themselves access to sensitive data.

Never Rest

The proper approach to network segmentation is to never say “completed.” Every network is subject to change – and so are the access controls governing connectivity. A continuous stepwise approach is best. Using NSPM, with each step, you have the opportunity to review, revise, and continue the momentum towards optimal segmentation. 

About the author: Reuven Harrison is CTO and Co-Founder of Tufin. He led all development efforts during the company’s initial fast-paced growth period, and is focused on Tufin’s product leadership. Reuven is responsible for the company’s future vision, product innovation and market strategy. Under Reuven’s leadership, Tufin’s products have received numerous technology awards and wide industry recognition.

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