What Is a CUI Enclave? How to Simplify NIST 800-171 & CMMC 2.0 Compliance

If you handle Controlled Unclassified Information (CUI) on behalf of the Department of Defense (DoD), you’ve probably spent a lot of time focused on how you can meet NIST 800-171 requirements and become CMMC (Cybersecurity Maturity Model Certification) compliant. But when it comes to meeting these requirements, implementing the controls is just a part of the challenge.

If you want to ensure your 75-person company is fully compliant with CMMC, it could mean overhauling your entire IT environment and implementing controls across every department and device within your organization. This is where a CUI enclave comes into play.

A CUI enclave is a cordoned off part of your IT environment designed specifically for handling CUI. An enclave isolates the sensitive data so the rest of your business can operate normally. In this guide, we’ll explain exactly what an enclave is, how it works, and how to decide if it’s the right route for your business.

What is CUI?

CUI is a category of sensitive Federal government information that is unclassified but still requires strict safeguarding and protection under regulations like DFARS 252.204-7012. While CUI isn’t classified information or top secret, the DoD still requires that it’s safeguarded security. Access to CUI requires a “lawful government purpose” and it needs to be protected in alignment with CMMC Level 2 requirements.

What is a CUI Enclave?

A CUI enclave is a dedicated, isolated, and strictly controlled physical or IT environment designed for the sole purpose of receiving, processing, and storing Controlled Unclassified Information. Think of it like a secure room built on the side of your office building where only those who truly need access can get inside.

Think of a CUI or CMMC enclave as a digital (or physical) safe room for sensitive information.

Its purpose is to stop CUI from sprawling across your entire company. Instead of letting sensitive data live on every laptop and server, you build a small, fortified environment designed with the primary purpose of protecting sensitive data and limiting its flow across your company.

Understanding where your business receives and processes CUI is one of the most important aspects of working towards CMMC Level 2 because it radically shrinks your audit scope.

Rather than proving every IT system, every employee laptop, and every physical office needing to meet CMMC's requirements, you only need to get the enclave audited. It’s the difference between securing a single vault and trying to secure the entire bank.

How to Decide When You Need a CUI Enclave for NIST SP 800-171 and CMMC

When it comes to protecting CUI under CMMC requirements you have two options:

1. Build an Enclave: Cordon off parts of your IT systems or physical space to protect CUI.
2. Go All-In: Ensure your full organization and infrastructure is compliant with CMMC Level 2 requirements for handling CUI. This is more suitable to organizations where CUI flows throughout (and involves a lot more work to achieve).

Here’s what you should consider when deciding which route to take:

1. Who Needs Access

This is the simplest test. Do you have 50 employees, but only three engineers and one PM who will ever touch CUI as part of a DoD contract? In this scenario, an enclave makes a lot of sense as you’re isolating the compliance burden from 50 users down to four.

2. Where CUI Data Flows

This is the most important technical question. Does the CUI need to be deeply integrated across your whole business or can it easily be contained within part of your system:

• The enclave approach makes sense if the CUI only flows through a certain part of your system (or can be contained to a certain part of your system easily). A CUI enclave can make NIST 800-171 and CMMC compliance much more straightforward as you only need to enforce the required controls across the environment that handles CUI rather than your entire system.
• Taking an all-in approach may work better if the DoD is a customer of your platform, and CUI will be flowing through your production CI/CD pipeline and servers. In this case, you’ll likely need to secure the whole system.

3. The Cost of Change

Can you afford to tell your entire sales team they can no longer use their personal phones for email? Can you ban USB drives for everyone in marketing? Can you enforce 15-character complex passwords and 60-minute screen locks on your CEO's laptop?

If the answer is "no," you need an enclave. It allows you to enforce these strict (and productivity-killing) controls on only the small group of users who must handle CUI, while letting the rest of the company operate with your usual, commercial-grade security.

How Does a CUI Enclave Work?

The goal of an enclave is to keep anything related to CUI separate from your main IT infrastructure. It means that when it comes to implementing NIST 800-171 controls and meeting CMMC 2.0 requirements, only the areas of your infrastructure that handle CUI will need to be audited.

When it comes to building an enclave, here are three things you’ll need to consider:

1. Identity Isolation: Your users must have separate, dedicated identities for the enclave. They cannot use their day-to-day name@company.com Google login to access the secure environment. They must use a completely separate, hardened credential which is managed in a separate user directory (like Azure Active Directory) with its own multi-factor authentication.
2. Asset Segregation: The enclave has its own infrastructure. It does not piggyback on your corporate IT. It has its own patch management, its own vulnerability scanning, its own logging (SIEM), and its own endpoint protection (EDR). You are, in effect, building a tiny, separate company from an IT perspective.
3. Data Flow Control: This is the most critical pillar. The boundary must be non-permeable. Data can come in (from the DoD or a prime contractor), but it cannot get out without an explicit, audited, and approved process. This means your enclave is configured to:‍
   
   1. Disable clipboard copy/paste from the enclave to the host machine.‍
   2. Block file downloads from the enclave to the local desktop.‍
   3. Prohibit USB drive access.
   4. Block access to all non-authorized web services (no personal Gmail, no Dropbox, no Slack).

How to Build a CUI Enclave

So what does a CUI enclave actually look like? The right option depends on your team, organization, and tech stack. Here are the most common setups:

• VDI/Virtual Desktop: Users log into a secure virtual machine (VM) that is pre-configured to meet CMMC requirements. All CUI work happens inside that VM, and the sensitive data never actually touches their local laptop.
• Cloud-based: You build a secure enclave within a dedicated, high-security government cloud environment from FedRAMP authorized cloud service providers like Microsoft 365 GCC High or AWS GovCloud.‍
• Managed Enclave Providers: You pay a specialized third-party provider (an MSP or MSSP) to build, manage, and maintain a pre-configured, compliant enclave for you.‍
• In-House Solutions: You use your own hardware and IT team to physically and logically segment a part of your own network, creating a secure mini-network where all CUI lives.

Safeguard CUI with Workstreet

CMMC is no longer optional. The final rule is in place and soon all defense contractors in the Defense Industrial Base (DIB) will need to meet CMMC compliance requirements.

If you’re looking to streamline your compliance efforts, a CUI enclave and compliance boundary is one of the most effective ways to simplify your progress towards meeting NIST 800-171 requirements and CMMC 2.0 compliance.

Workstreet offers expert-led implementation of CMMC, FedRAMP, GovRAMP, CJIS, NIST 800-171, and NIST 800-53 frameworks. Get certified faster with our automation-first services and dedicated public sector specialists. Speak to an expert about how we can help here.