Microsegmentation Is Critical, CISA Says. Here’s How You Can Get It Done.

Look at any recent cybersecurity framework or strategy, and you’ll spot a common thread: microsegmentation is no longer optional. It’s foundational.

The federal government just made that clearer than ever. In its July 2025 report, The Journey to Zero Trust: Microsegmentation in Zero Trust — Part One, CISA outlines the critical role microsegmentation plays in limiting lateral movement, containing breaches, and enforcing Zero Trust principles.

For most federal security teams, this isn’t a surprise. It’s a continuation of a much-needed shift.  

Legacy, perimeter-based defenses and network-based segmentation solutions aren’t enough anymore. And while SASE solutions have their place, attackers don’t just break in. They move around. Microsegmentation is what keeps them contained.

In this post, we’ll break down CISA’s latest guidance, what it means for federal agencies, and how Illumio can help you meet and accelerate your microsegmentation goals.

Microsegmentation is now a must

CISA’s latest report is a call to action for federal agencies.  

Traditional network segmentation tools like VLANs and firewalls assume trust based on location. But Zero Trust assumes compromise. Every request must be verified, and every connection must be isolated.

In the report, CISA puts it simply: “The transition to Zero Trust requires more than a shift in technology — it demands a shift in security culture.”

That’s why the report recommends a phased, organization-wide approach to microsegmentation. Agencies must:

• Identify high-value resources and their dependencies.
• Create granular, risk-informed segmentation policies.
• Deploy policy enforcement at the host, application, or service level.
• Ensure ongoing visibility and centralized control.

This guidance is intended for federal civilian executive branch (FCEB) agencies. But the truth is, any organization moving toward Zero Trust should take notice.

Microsegmentation is a mission-enabler

CISA highlights microsegmentation as a critical way to protect modern, highly complex environments.  

Microsegmentation allows agencies to apply the right controls where they matter most: around specific systems, workflows, and sensitive data.

Done right, microsegmentation delivers:

• Smaller attack surfaces for adversaries to exploit ‍
• Granular control over which resources can talk to each other and when ‍
• Faster detection and containment of breaches ‍
• Stronger compliance with EO 14028 and M-22-09 mandates

As CISA puts it, microsegmentation doesn’t replace defense-in-depth but rather enhances it. Think of it as the smart, adaptive layer that aligns security controls with mission-critical operations.

How can Illumio help

CISA’s report outlines a four-phase approach to microsegmentation:

1. Identify candidate resources
2. Map their dependencies
3. Define appropriate policies
4. Deploy and iterate

This is exactly the process Illumio supports — with one major upgrade: automation and visibility every step of the way.

With the Illumio platform, you can segment in days, not months. You get centralized control across mixed environments, and you can validate that every policy is working in real time.

It’s why Illumio was named a Leader in The Forrester Wave™: Microsegmentation Solutions, Q3 2024. And it’s why more agencies are adopting Illumio as the foundation for their Zero Trust architectures.

Here’s how the Illumio platform, including Illumio Segmentation and Illumio Insights, can help you meet — and exceed — CISA’s microsegmentation recommendations.

Illumio Segmentation: modern microsegmentation made simple

If you’re wondering how to move from static firewalls and perimeter-based defenses to dynamic, policy-driven segmentation, you’re not alone.

That’s exactly where Illumio Segmentation helps federal agencies lead.

Illumio Segmentation is purpose-built to deliver microsegmentation for today’s complex networks. It helps you build granular Zero Trust controls without relying on legacy network constructs.  

With Illumio Segmentation, you can:

• Visualize your environment with a real-time application dependency map, so you know exactly what’s talking to what. ‍
• Segment with precision using policy that follows workloads across data centers, clouds, endpoints, and hybrid environments. ‍
• Contain threats fast by instantly enforcing policies that block lateral movement.

Unlike traditional segmentation methods, Illumio doesn’t rely on network devices or static IPs. It uses identity and context to define segmentation at the workload level. This makes it resilient, scalable, and easier to manage than segmentation of the past.

As CISA recommends, segmentation must go beyond the perimeter. Illumio lets you enforce security controls where the workloads live, not just at the network edge.

Illumio Insights: see, understand, and prioritize risk

Before you can segment, you need to understand your environment.

That’s where Illumio Insights comes in.

Illumio Insights gives you instant visibility into unmanaged workloads, misconfigurations, and excessive access across your infrastructure. It then offers you recommendations based on real traffic patterns and attacker behavior.

Illumio Insights helps agencies:

• Identify segmentation candidates aligned with business priorities
• Detect lateral movement risk before an attack spreads
• Continuously validate that segmentation policies are enforced correctly

Combined with Illumio Segmentation, Insights acts as your microsegmentation mission control. It shows you where to start, how to prioritize, and what to fix first.

Agencies can’t delay microsegmentation

CISA’s July 2025 document is the first of two. A more technical guide is coming soon. But agencies shouldn’t wait to implement microsegmentation as part of their Zero Trust strategy.

The mandate is clear. EO 14028 and OMB M-22-09 require agencies to “meaningfully isolate environments” to stop lateral movement and contain threats and outline three enforcement points: device/user, SASE, and microsegmentation.

Microsegmentation is no longer a nice-to-have. It’s table stakes for Zero Trust.  

Leaders must act now to define their microsegmentation strategy, select scalable solutions like Illumio, and build security that keeps attackers contained.

Discover how Illumio can help you achieve CISA’s guidance.