If your organization handles CUI, one of the most consequential decisions in your compliance journey is how much of your IT environment falls into scope. Every system, user, and application that touches CUI must meet the full set of NIST SP 800-171 requirements. For many defense contractors, the answer to that scoping challenge is a CUI enclave.

What is a CUI enclave?

A CUI enclave is a logically or physically isolated portion of your IT environment where all systems that store, process, or transmit CUI are confined. Think of it as a secure room within your larger facility: only those with a need-to-know get access, and everything inside is held to a higher security standard.

The Cyber AB's CMMC Assessment Process formally defines an enclave as "a set of system resources that operate within the same security domain and that share the protection of a single, common, and continuous security perimeter." The key phrase is technically enforced: an enclave is a boundary maintained through firewalls, network segmentation, access controls, and monitoring. Not just a policy that says CUI should stay in certain places.

A CUI enclave includes:

• Any system that stores, processes, or transmits CUI, including file servers, databases, and email platforms
• The authorized users who access or handle CUI
• The applications used to generate, view, or share CUI, from CAD software to communication tools

No CUI should enter or leave the enclave without proper encryption and security controls. That applies to data transfers, backups, and printed documents alike.

How CUI enclaves reduce compliance scope

If CUI is scattered across shared drives, commercial SaaS tools, laptops, and collaboration platforms, your CMMC compliance footprint expands to match: more endpoints to configure and monitor, more users requiring CUI training, more privileged accounts to manage, and more evidence to produce to support an assessment.

An enclave solves this by consolidation. You only have to apply the NIST SP 800-171 requirements to the systems inside the boundary, and everything outside it stays out of scope. 

For small and mid-sized defense contractors especially, this shift can significantly reduce complexity, licensing costs, and long-term compliance overhead. It's one of the most practical strategies available for meeting CUI safeguarding requirements without turning your entire infrastructure into a compliance project.

Common CUI enclave models

Most organizations implement one of a few approaches:

• Cloud-based enclave in a FedRAMP Authorized environment such as AWS GovCloud, Microsoft Azure Government, or Microsoft 365 GCC High
• Virtual desktops, where users access CUI only through a secure virtual desktop session and CUI never resides on local devices
• Encrypted overlay, a dedicated encrypted layer for CUI communications and storage alongside commercial tools for everything else
• Physical enclave, with dedicated hardware and a segmented internal network reserved exclusively for CUI

When does a CUI enclave make sense?

An enclave isn't the right fit for every organization. As a general rule, it makes the most sense when a relatively small percentage (30% or less) of your workforce handles CUI and federal contracts represent a meaningful but not dominant portion of your revenue. If most of your team touches CUI regularly and the majority of your work is federal, applying controls enterprise-wide may actually be simpler than maintaining two separate environments.

The decision comes down to weighing your compliance needs against your resources, risk tolerance, and day-to-day operations. In the next article in this series, we look at the specific benefits a secure CUI enclave delivers, and the situations where it's the clear right choice.