Sharing how Microsoft now secures its network with a Zero Trust model

Apr 22, 2021   |  

Editor’s note: We’ve republished this blog with a new companion video.

Safeguarding corporate resources is a high priority for any business, but how does Microsoft protect a network perimeter that extends to thousands of global endpoints accessing corporate data and services 24 hours a day, seven days a week?

It’s all about communication, collaboration, and expert knowledge.

Phil Suver, senior director of networking at Microsoft, and his team help champion Zero Trust networking, an important part of Microsoft’s broader Zero Trust initiative. Driven by Microsoft’s security organization, the Zero Trust model centers on strong user identity, device-health verification, application-health validation, and secure, least-privilege access to corporate resources and services.

“Zero Trust networking is ultimately about removing inherent trust from the network, from design to end use,” Suver says. “The network components are foundational to the framework for our Zero Trust model. It’s about revising our security approach to safeguard people, devices, apps, and data, wherever they’re located. The network is one piece. Identity and device health are additional pieces. Conditional access and permission are also required. That involves the entire organization.”

Indeed, this extensive initiative affects all of Microsoft and every employee. To support the Zero Trust initiative, Microsoft’s network engineering team is partnering with the security and end-user experience teams to implement security policy and identity while ensuring productivity for employees and partners. Suver says that his team always aims to minimize those impacts and communicate how they ultimately result in benefits.

“We’re fundamentally changing the way our network infrastructure has worked for more than two decades,” Suver says. “We’re moving away from internal private networks as the primary destination and toward the internet and cloud services as the new default. The security outcomes are the priority, but we have to balance that against business needs and productivity as well so that connectivity is transparent.”

That means being sensitive to how implementing Zero Trust networking affects users on a granular level, to ensure that employees don’t experience work stoppages or interruptions.

“Some of our efforts aren’t very disruptive, as they’re simply accelerating in a direction we were already heading,” Suver says. “Shifting to internet-first and wireless-first network design, and enabling remote work are examples of that. Others are indeed disruptive, so we work closely with the affected groups to help them understand the impact.”

Suver notes that understanding and communication are critical to avoiding disruption.

“Microsoft is an established enterprise, with some software and systems that have been in place for decades,” he says. “To run our business effectively, we must be able to accommodate processes and technology that might not be immediately ready to transition to a Zero Trust architecture.”

We’re able to be a little more opportunistic and aggressive with our in-building connectivity experiences while our user base is working remotely. This has allowed us to roll out configurations and learn things with a much smaller user population on-campus.

– Phil Suver, senior director of networking

Suver stresses the importance of working closely with affected employees. “We need to partner closely with our engineering teams to understand their connectivity requirements and build solutions around those for the short term and then broaden our scope for the longer term.”

With more employees working from home than ever due to COVID-19, many deployments in Microsoft buildings have been implemented relatively quickly and efficiently because of the decreased on-campus presence. Engineering teams can perform rollouts, including deploying new network segments, creating new wireless connections, and deploying network security policy with much less disruption than if buildings were fully occupied.

“We’re able to be a little more opportunistic and aggressive with our in-building connectivity experiences while our user base is working remotely,” Suver says. “This has allowed us to roll out configurations and learn things with a much smaller user population on-campus.”

[Check out these lessons learned and best practices from the Microsoft engineers who implemented Zero Trust networking. Find out what Microsoft’s leaders learned when they deployed Zero Trust networking internally at the company. Read Brian Fielder’s story on how Microsoft helps employees work securely from home using a Zero Trust strategy.]

Managing Zero Trust networking across the enterprise

Mildred Jammer, Zero Trust network principal program manager at Microsoft, acknowledges that the inherent complexity of Microsoft’s operations—there are more than 1 million devices on Microsoft’s network, which supports more than 200,000 employees and partners, which requires a highly strategic planning approach to transition to a Zero Trust environment.

“It’s a huge scope, and we have so many different environments to consider. Unsurprisingly, planning is a top priority for our teams,” says Jammer, whose work centers around ensuring that people and functional groups across Microsoft unite to ensure that Zero Trust Networking initiatives receive the priority that they deserve.

Zero Trust networking goals include reducing risk to Microsoft by requiring devices to authenticate to achieve network access providing a network infrastructure that supports device isolation and segmentation. A third key goal is to devise a system for enhancing response actions if devices are determined to be vulnerable or compromised.

“Zero Trust networking extends beyond the scope of Microsoft networking teams,” Jammer says.

Jammer says that many business groups at Microsoft might not understand what Zero Trust networking is, or they might not consider it as important as other initiatives they’re supporting.

“Zero Trust networking is a huge priority for our teams, but our business groups have their own priorities that don’t account for Zero Trust,” Jammer says. “Neither priority is optional, and they may conflict. We must manage that.”

She says communication being upfront with requirements, and collaborating willingly across Microsoft to ensure everyone’s needs are met.

Jammer says that distilling high-level goals into smaller, more achievable objectives helps employees and partners understand the practicalities of Zero Trust networking so that her teams can establish realistic expectations. “For example, we worked with the security team to break down risk mitigation into specific risks and the outcomes,” she says. “We developed solutions to deliver the outcomes and grouped them when there were commonalities. If business priorities challenged our outcomes, we could break down those groupings, as necessary.”

Jammer cites the deployment of Zero Trust networking as an example, noting that her team initially planned to deploy globally across all wired and wireless networks.

“We planned for a full deployment, but soon learned how disruptive that would be to our developers and infrastructure,” she says. “So, we broke it into chunks, we implemented changes to wireless networks with internet-first posture, and then came back to address our wired networks. To minimize impact and identify best practices, we used flighting deployments with a ring-based approach, starting with a smaller, well-understood population that closely represented our larger target population. As we gained more experience and confidence, we expanded the deployment to reach a larger population.”

Jammer notes that using targeted, achievable goals not only help get work done but also help identify when larger goals might be challenging to accomplish.

“Breaking down large goals into an agile-friendly process was also crucial to demonstrate areas that simply weren’t achievable near term,” Jammer says. “It’s more concrete and actionable to tell someone that we can’t refactor a specific app to be internet-facing than it is to say that we can’t eliminate our corporate intranet infrastructure.”

Making Zero Trust networking a reality

For David Lef, Zero Trust principal IT enterprise architect at Microsoft, implementing Zero Trust networking in a live networking environment carries a significant challenge.

“Reducing risk is a big focus in Zero Trust, but we need to do so with as minimal impact to user experience and productivity as possible,” Lef says. “Our users and employees need this network to perform their job functions. There is a reality that some things have to continue to work in their current state.”

Lef cites a few examples, including printers that didn’t support internet connectivity, IoT devices that required manual configuration, and simple devices that didn’t support Dynamic Host Configuration Protocol (DHCP). “We isolate those on the network and potentially come back to them later while we address projects that are ready to adapt to Zero Trust.”

Lef’s team actively works to establish network access, implement policies, segment networks, and onboard Microsoft business groups, regions, and teams to the Zero Trust networking model. While Zero Trust networking is critical to enabling a Zero Trust model, enterprise-wide collaboration and adoption are equally vital.

“We put a lot of effort into observing activity and talking with our local IT representatives about the details and challenges of each phase of our implementation,” Lef says. “We created our deployment plans so that employees and partners could naturally adopt the new network designs and usage patterns without significant effort on their part.”


Lef and Suver discuss how Microsoft helps its employees stay productive while working remotely.

Lef notes that his team recommends best practices to partners and suppliers to help build Zero Trust-friendly products and solutions.

“Making legacy technology conform to Zero Trust is difficult. We want to adopt solutions built for Zero Trust networking across our entire enterprise as much as possible. Identities, devices, apps, data, infrastructure—they all contribute to the model, along with networking,” Lef says. “Across the organization, all of these need to be in place for a properly functioning Zero Trust model.”

Thinking about the broader picture

Soumya Subramanian, partner general manager of enterprise infrastructure services at Microsoft, recognized a need to bring multiple workstreams together to accommodate the size and scope of deploying Zero Trust networking.

As organizations consider the scope of what they want to achieve with Zero Trust, they should remember to think about other network modernization initiatives and be intentional in either combining them under the broader program or allowing them to operate independently.

– Soumya Subramanian, partner general manager of Enterprise Infrastructure Services

Soumya Subramanian looks at the camera and smiles.
Soumya Subramanian is a partner general manager of Enterprise Infrastructure Services at Microsoft. (Photo submitted by Soumya Subramanian)

“We already had a workstream in flight to move remaining applications from the corporate network to the cloud” Subramanian says. “We also needed to accelerate our long-term plans for remote connectivity due to the pandemic, which allowed us to reevaluate remote access technologies under the context of Zero Trust. For instance, as you move high-volume applications off the corporate network and onto the cloud, you reduce VPN volumes and usage. You need to consider alternate remote connectivity solutions like Secure Access Service Edge (SASE), virtual desktops, and application proxy services in your Zero Trust networking scope, not just the in-building user experience.”

Subramanian notes that these efforts depend on network automation and data-collection workstreams that many organizations could use to accelerate Zero Trust deployment.

“We started to tie these efforts together so that the network designs and policies we created for Zero Trust could be managed through automation at scale. As a result, we’re more data driven with clear objectives and key results that connect these dependent workstreams.”

“As organizations consider the scope of what they want to achieve with Zero Trust, they should remember to think about other network modernization initiatives and be intentional in either combining them under the broader program or allowing them to operate independently,” Subramanian says.

Check out these lessons learned and best practices from the Microsoft engineers who implemented Zero Trust networking.

Find out what Microsoft’s leaders learned when they deployed Zero Trust networking internally at the company.

Read Brian Fielder’s story on how Microsoft helps employees work securely from home using a Zero Trust strategy.

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