DoD IL6 Requirements: Infrastructure, SIPRNet, and Authorization

DoD Impact Level 6 (IL6) requirements are the security rules in the Department of Defense Cloud Computing Security Requirements Guide (CC SRG) that a cloud service must satisfy to store and process classified information up to the Secret level. In short: dedicated infrastructure inside U.S. facilities cleared for classified processing, network access only through SIPRNet, FIPS 140-3 encryption paired with NSA-approved solutions for classified data, an operations staff of cleared U.S. citizens, and a FedRAMP High baseline layered with DoD-specific controls, all validated through a DISA Provisional Authorization and monitored continuously afterward.¹

What IL6 Covers and Why It’s Different

IL6 sits at the top of the CC SRG’s impact-level hierarchy. IL2 covers non-controlled unclassified data. IL4 covers Controlled Unclassified Information. IL5 covers higher-sensitivity CUI, mission-critical data, and certain National Security Systems, and is the highest level for unclassified information. IL6 is the level for classified information up to Secret on National Security Systems.²

The step from IL5 to IL6 is not incremental. IL5 still runs on unclassified networks; IL6 crosses into classified territory, which triggers a different facility posture, a different network, and a different personnel standard. A provider authorized at IL5 cannot simply bolt controls onto that environment to reach IL6. It needs a separate classified build from the ground up.

Dedicated Infrastructure in U.S. Facilities

An IL6 environment must run on dedicated infrastructure inside facilities approved for processing classified information at or above the Secret level. The January 2025 CC SRG defines an IL6 environment as a “closed self-contained environment” that covers the processing, storage, and management planes.¹ The hardware hosting IL6 workloads cannot be shared with commercial, state, or local government customers.

Physical separation from non-DoD and non-federal tenants is mandatory. Between DoD and other federal tenants, the SRG permits virtual or logical separation. Between individual mission systems inside the IL6 environment, logical separation is the minimum. One IL6 cloud can therefore support multiple Secret-level missions from different DoD organizations, provided the underlying infrastructure is physically walled off from anything outside the federal government.

Location matters as well. Control SA-9(5) restricts information processing, data, and system services to locations under U.S. legal jurisdiction. That covers primary storage, backups, disaster recovery sites, and management networks. The SRG makes no exception for temporary transfers or foreign failover.

Connectivity Only Through SIPRNet

IL6 environments operate as enclosed SIPRNet enclaves. The CC SRG treats both on-premises and off-premises IL6 offerings as extensions of the SIPRNet boundary, describing them as “one or more closed SIPRNet enclaves” whose virtual fence line surrounds the whole cloud environment.¹ No traffic reaches the public internet.

For IL4 and above, commercial cloud services must connect through the Defense Information Systems Network (DISN) using an Enterprise Cloud Access Point or a Component-level access point approved by the DoD CIO. The Secure Cloud Computing Architecture supplies the surrounding framework, including Boundary Cloud Access Points for traffic filtering and intrusion detection, and Virtual Datacenter Security Stacks for firewalling, intrusion prevention, and web application security.³ At IL6, those protections sit inside the classified network boundary rather than on NIPRNet.

Encryption: FIPS 140-3 Plus CSfC

Data at rest and in transit inside an IL6 environment must be protected with cryptographic modules validated under FIPS 140-3, the NIST standard for cryptographic module security.⁴ FedRAMP enforces FIPS 140-3 compliance during authorization, and the DoD’s FedRAMP+ model carries the requirement forward at every impact level.⁵

Because IL6 handles classified data on National Security Systems, encryption obligations go further. The NSA’s Commercial Solutions for Classified (CSfC) program controls how commercial encryption products can protect classified information. Solutions must follow specific Capability Packages published by NSA and be registered with the agency before deployment on national security networks.⁶ Key management follows standardized protocols, and any physical storage device leaving the classified environment stays unintelligible without the proper keys.

Cleared U.S. Personnel Only

Everyone who touches an IL6 system must be a U.S. citizen, U.S. national, or U.S. person, and must hold an active security clearance at Secret or above. The January 2025 SRG’s personnel screening control (PS-3(4)) separates users from administrators. Users may include foreign personnel only with explicit Authorizing Official approval and compliance with current DoD policies. Administrators must be U.S. citizens, nationals, or U.S. persons, with no foreign personnel exception.¹ This applies to anyone with administrative access or physical proximity to the hardware.

Obtaining a Secret clearance requires a background investigation. Under the older model, Secret clearance holders faced reinvestigation every ten years. The DoD has enrolled all personnel in continuous vetting, which monitors criminal records, financial activity, and foreign travel on an ongoing basis rather than waiting for a scheduled cycle.⁷ Losing a clearance at any point means immediate loss of system access.

The FedRAMP+ Control Baseline

The DoD does not write its cloud security controls from scratch. It uses a FedRAMP+ approach: start with the FedRAMP baseline for the impact level, then layer DoD-specific controls on top.² For IL6, the required baseline is FedRAMP High, which maps to NIST SP 800-53 security controls. The January 2025 SRG states that “FedRAMP High is the requirement for NSS and Classified information up to Secret for DOD cloud services.”

Layered on top are DoD parameter values and additional controls: stricter account lockout for privileged users (three failed attempts before an administrator must unlock the account), DoD-specific cryptographic key management tied to DoD PKI policy, and additional maintenance and supply chain controls. Existing IL5 and IL6 offerings were required to update to NIST SP 800-53 Revision 5 by the end of calendar year 2025, with a plan of action due within 30 days of the SRG’s January 2025 publication.¹

CNSSI 1253 governs control selection for National Security Systems. Unlike the standard federal approach that applies a single “high water mark” across confidentiality, integrity, and availability, CNSSI 1253 preserves three separate impact values. That is why IL6 authorizations are often described with notation like “H-H-x,” meaning high confidentiality, high integrity, and availability determined by the customer.⁸

How a Provider Gets Authorized

There are two routes to a DoD Provisional Authorization at IL6: leverage an existing FedRAMP authorization, or have a DoD component sponsor the offering directly.⁹ Both paths converge at DISA for final review and PA issuance; they differ in how the initial assessment work gets done.

Under the FedRAMP leverage path, a provider with an existing FedRAMP High authorization builds on that assessment, and the DoD evaluates whether the additional DoD-specific controls are also met. Under the DoD sponsorship path, a DoD component sponsors the offering through authorization and submits a request through the DoD Cloud Authorization Services (DCAS) site to start the process.

SSP and 3PAO Assessment

Either way, the provider must produce a System Security Plan. FedRAMP describes the SSP as the “security blueprint” for the cloud offering, mapping architecture, data flows, control implementations, and the authorization boundary in enough detail for a government reviewer to trace every claim.¹⁰ For an IL6 environment, the SSP typically runs into hundreds of pages because of the added classified-system controls and facility documentation.

An independent Third-Party Assessment Organization (3PAO) then audits the system to verify the SSP’s claims. At IL6, the 3PAO needs the facility clearance and personnel clearances required to assess a classified environment. If a provider engaged a 3PAO in an advisory role during SSP development, a different 3PAO must perform the independent assessment.

DISA Review, PA, and Component ATO

The completed package (SSP, 3PAO results, supporting artifacts) is submitted to DISA through the Cloud eMASS system. DISA validates the results and decides whether the offering meets every CC SRG requirement for the requested impact level.¹¹ Review time depends on system complexity and submission quality; providers should expect many months.

If the offering passes, DISA’s Authorizing Official issues a Provisional Authorization. A PA is not an open-ended approval to host any DoD mission. It confirms the cloud offering meets security requirements. Each DoD component must still grant its own Authorization to Operate (ATO) for its specific mission and data before using the service. The PA addresses inherent risk in the offering; the ATO addresses mission-specific risk. The DoD also reserves the right to conduct penetration testing on any IL6 environment at any time, using methods of its choosing.

Continuous Monitoring After Authorization

A PA starts an ongoing obligation. Every offering with a DoD PA must comply with continuous monitoring, including monthly reporting and annual reassessments.¹¹

Vulnerability remediation runs on set timelines: high-severity findings within 30 days of discovery, moderate within 90 days, and low within 180 days. Progress is tracked through a Plan of Action and Milestones, and DISA monitors compliance. Any significant change to the system’s architecture, security boundary, or control implementation must be reported immediately. Missing remediation timelines or reporting requirements puts the PA at risk of suspension or revocation.

What It Costs

The CC SRG does not set pricing, but IL6 is among the most expensive compliance efforts in cloud computing. FedRAMP High authorization alone, which serves as the IL6 baseline, carries estimated initial costs from $1 million to more than $3 million once consulting, engineering, documentation, 3PAO assessments, and continuous monitoring setup are counted. Ongoing annual costs at FedRAMP High run between $500,000 and $1 million. IL6 then adds classified-rated facilities, cleared personnel, SIPRNet connectivity, and NSA-approved encryption, pushing total investment well beyond those baseline figures.

For a DoD mission owner rather than a provider, the equation shifts. The provider carries the infrastructure and authorization cost. The mission owner still pays for its own ATO, training cleared personnel to use the environment, and continuous monitoring tied to its specific deployment.

1
Defense Information Systems Agency. Cloud Service Provider Security Requirements Guide
2
Cloud Information Center – GSA. Cloud Security
3
Department of Defense Chief Information Officer. DoD Cloud Security Playbook Volume 1
4
National Institute of Standards and Technology. FIPS 140-3 Security Requirements for Cryptographic Modules
5
FedRAMP. Strengthening the Use of Cryptography to Secure Federal Cloud Systems
6
National Security Agency. Commercial Solutions for Classified Program (CSfC) Frequently Asked Questions
7
U.S. Department of Defense. All DOD Personnel Now Receive Continuous Security Vetting
8
National Security Agency. Security Categorization and Control Selection for National Security Systems
9
Cyber Exchange. DoD Cloud Computing Security
10
FedRAMP. System Security Plan (SSP)
11
Defense Information Systems Agency. DoD Cloud Authorization Process