Network segmentation best practices (how to implement)

Your network segmentation strategy has a broad impact on security policies and processes throughout your organization. It defines your organization’s attack surface and establishes the level of difficulty hackers will face when trying to gain network access.

Optimized enterprise networks also correlate strongly with productivity and performance gains. If your computer network reduces data congestion, prioritizes critical traffic flows, and optimizes bandwidth usage, you will see marked improvement in network performance.

However, poorly segmented networks can have the opposite effect, too. Following the best practices for network segmentation ensures every part of the network operates securely and efficiently.

There are many ways you can divide your network into discrete, functional domains. Finding the right connectivity balance between network segments is key to optimizing your security posture.

Physical vs. logical: Two types of network segmentation explained

Before the development of cloud computing and IoT technology, all networks were segmented physically. Now, organizations can implement logical segmentation using software-defined networking and virtual local area networks (VLANs).

Most networks share some elements of both. Let’s look at how the segmentation process looks like for these two types of networks:

• Physical segmentation divides a network into separate subnetworks and controlling access with firewalls. The internal network is defined by the configuration of routers, hubs, and endpoints that make it up.
• Logical segmentation divides a network into subnets using VLANs and network addressing schemes. Even though subnets may be physically located in a completely different data center, they are designed to share similar network resources.

It’s usually easier to implement a network segmentation plan using physical segmentation. However, it’s also more expensive and less scalable because the organization must buy, deploy, and maintain physical equipment on-premises.

This lack of flexibility is important for security leaders because it limits the types of security controls they can put in place. For example, if the organization needs to change its network configuration to achieve PCI DSS compliance, it might have to wait until it has the resources, equipment, and specialist talent needed to do so.

Logical segmentation is much more flexible. Security zones, access control permissions, and other security measures can be configured on the fly. It’s possible to completely modify the entire network without ordering new equipment.

That flexibility is important in today’s fast-moving cybersecurity landscape. Organizations that wish to leverage the benefits of network segmentation to implement Zero Trust architecture have a clear incentive to use logical segmentation whenever possible.

How to implement network segmentation

Every organization is unique, so there are no one-size-fits-all rules for achieving optimal network segmentation. However, there are some common network security rules that can help organizations protect sensitive data while avoiding over-segmentation:

1. Categorize business assets by risk

Before making any changes to the way your organization handles network traffic, take time to categorize all business assets and prioritize them according to risk.

High-risk assets that hold sensitive data should be treated separately. They should have fewer third-party access points and a reduced attack surface compared to every other part of the network.

Once you have assigned a risk category to every business asset, you can begin separating them into use cases and domains. Consider how each individual network segment would respond to a malware attack or data breach. How would it impact the rest of the organization and its third-party service providers?

2. Implement the principle of least privilege

Every user in your network should only have access to the segments they need access to. This prevents lateral movement and makes it harder for hackers to launch catastrophic cyberattacks against multiple segments at once.

Many organizations with low network requirements have a relatively flat network structure. The principle of least privilege describes a more rigid hierarchy of access, where only admin-level users have broad network permissions.

Even then, bad actors can (and will) target high-level administrator accounts whenever they can. These accounts should be treated as high-risk assets and given the appropriate security controls to protect against known and unknown vulnerabilities.

3. Group similar assets together

Assets that serve the same groups of users and have similar risk profiles should be assigned to the same network segment when possible. These segments will usually correspond to well-established business functions like accounting, sales, and production.

However, if you pay close attention to how your organization actually works on a day-to-day basis, you may see unexpected groupings occur. If your marketing department frequently accesses manufacturing data to publish customer-facing webinars, you may wish to group them together in your segmentation plan.

Avoid the temptation to create as many segments as possible. There is a difference between micro-segmentation and over-segmentation. Putting individual assets in their own segment can make sense in certain scenarios, but it will also impact the usability of those assets.

4. Don’t forget about legitimate users – or their expectations

Security professionals typically think of network segmentation in terms of blocking hackers from compromising network assets. However, there is often a trade-off between security and usability, and legitimate users should enjoy a friction-free experience when possible.

If you over-segment your network, you run the risk of pushing legitimate users to use shadow IT applications. If they simply bypass security policies they don’t like, you won’t have any visibility into their network activity at all.

Shadow IT can be as simple as a customer service representative reaching out to a customer using WhatsApp instead of the company’s help desk client. Consider reaching out to users and soliciting their feedback on security policies so you can maintain buy-in and compliance.

5. Restrict third-party access

Almost all organizations require some degree of third-party access. Vendors, partners, and service providers often need to interact with network assets directly. Many organizations deploy APIs specifically for that purpose.

But that doesn’t mean you should automatically trust third-party service providers. In fact, you should restrict their access according to the Zero Trust model. This protects you from attack scenarios where attackers compromise their systems first – and then move on to attack yours.

Defining the scope of third-party restrictions can be challenging. Penetration testing can give you valuable data on exactly how vulnerable your third-party connections are, and what kinds of security controls can help safeguard them.

5 Benefits of optimized network segmentation

When implemented correctly, network segmentation provides a range of security benefits to organizations.

1. Improved data privacy

Properly segmented networks keep confidential data separate from low-risk data. When your network architecture limits connectivity between your high-risk assets and the rest of the network, it helps improve data privacy and reduce the chance of cyberattack.

By helping achieve data privacy, network segmentation plays a major role helping organizations achieve compliance with data privacy regulations like PCI DSS. Even though the regulation does not specifically require segmentation, it strongly recommends organizations segment their networks to improve data privacy while lowering costs.

2. Slower network intrusions

When hackers successfully attack a well-segmented network, they quickly come up against robust barriers between them and their goals. If incident response teams notice the intrusion quick enough, bad actors may already be isolated and quarantined inside the compromised network segment.

But even if they are not, they still have to confront the barriers segmentation presents. This typically generates a higher volume of alerts, corresponding to more accurate alarms and visibility into active attacks.

3. Better monitoring performance

Whenever a user passes from one network segment to another, it generates a log. That log can help security professionals work conduct forensic investigations in response to intrusions and cyberattacks.

Security Information and Event Management platforms help organizations make the most of their log data by providing a centralized location to store and analyze logs for evidence of cyberattack. A properly segmented network will generate a higher volume of better-quality logs than a poorly segmented one.

4. Increased IoT security

Organizations that rely on a fleet of IoT devices need to make sure those assets are covered by a comprehensive security policy. These devices typically do not come with robust internal security controls, which makes them a valuable target of opportunity for hackers.

By rearranging your internal network to keep IoT devices on their own subnet, you can reduce the attack surface these devices represent in your overall security posture. If bad actors compromise this network, they won’t be able to escalate their attack through other network segments very easily.

5. Faster incident response

Security operations personnel can’t mitigate cyberattacks if they don’t know exactly where network intrusions have occurred. Highly segmented networks offer a wealth of data telling security analysts exactly where and when unauthorized activity took place. This makes it easier for them to run incident response playbooks.

Security personnel equipped with automation-ready incident response technologies can even program playbooks to launch the moment unauthorized activity is detected. This combination maximizes the benefits of network segmentation while helping organizations achieve operational security excellence.