Securing Kubernetes Clusters in Federal Government Environments: A Technical Guide

Before diving into the technical details, it’s important to note that securing Kubernetes in DoD and federal government environments requires adherence to specific standards and frameworks unique to these settings. This comprehensive guide provides a detailed roadmap for implementing security measures across different impact levels while ensuring compliance with government requirements.

Understanding DoD Impact Levels

The foundation of any government Kubernetes security implementation begins with understanding the appropriate Impact Level (IL) classification for your data and applications, as this determines the security controls required.

Impact Level Classification Framework

The DoD classifies cloud security by Impact Levels based on data sensitivity and potential impact if compromised:

Impact Level 2 (IL2):

• Hosts publicly releasable or non-sensitive unclassified data
• Follows FedRAMP Moderate baseline requirements
• Allows minimal access controls (user ID/password authentication)
• Data can reside outside U.S. territories

Impact Level 4 (IL4):

• Hosts Controlled Unclassified Information (CUI) and mission data
• Unauthorized disclosure could cause serious adverse effects
• Requires FedRAMP High baseline plus 38 additional DoD-specific controls
• Restricts access to U.S. Persons with proper background checks
• Systems must operate within U.S. territories
• Requires NIPRNET connectivity

Impact Level 5 (IL5):

• Hosts higher-sensitivity CUI and Unclassified National Security Information (U-NSI)
• Adds nine additional controls beyond IL4
• Restricts access to U.S. citizens only (stricter than IL4)
• Requires hardware token technology with multifactor authentication
• Mandates physical and logical separation of government data from non-federal entities

Impact Level 6 (IL6):

• Handles classified information up to SECRET level
• Implements highest security controls
• Requires SIPRNet connectivity
• Restricts access to U.S. citizens with SECRET clearances

Understanding these impact levels is essential as they dictate the security requirements your Kubernetes implementation must satisfy.

DoD Kubernetes Reference Architectures

DoD has developed specific reference architectures for Kubernetes deployments in government environments.

DoD Enterprise DevSecOps Reference Design: CNCF Kubernetes

This reference design outlines the key architectural components required for a compliant Kubernetes deployment:

1. Cloud Native Access Point (CNAP): Manages all north-south network traffic within the infrastructure layer
2. Conformant Kubernetes Installation: Must use properly certified Kubernetes implementations that have submitted conformance testing results to CNCF
3. Centralized Artifact Repository: Must integrate with Iron Bank, the DoD Centralized Artifact Repository of hardened containers
4. Service Mesh: Required within the Kubernetes orchestrator to manage all east-west network traffic
5. Sidecar Container Security Stack (SCSS): Mandatory implementation to achieve zero-trust security down to the container/function level

Multi-Cluster Kubernetes Reference Design

For more complex environments, the Multi-Cluster Kubernetes Reference Design provides additional guidance:

1. Immutable Infrastructure: Kubernetes clusters must be designed to be scaled up, destroyed, or replaced rather than modified in place
2. Global Control Plane: Implements a global view across enclaves, allowing workloads to follow a clear path to production, even in disconnected or limited connectivity environments

These reference architectures establish the foundation for secure Kubernetes deployments in government environments.

Kubernetes Cluster Hardening

Cluster hardening in government environments typically follows the DISA STIG requirements and CIS Kubernetes Benchmarks.

DISA Kubernetes STIG Requirements

The DISA Kubernetes STIG version 1 release 11 contains 91 rules, categorized into different areas:

Control Plane Configuration

Critical control plane security requirements include:

• Disable anonymous authentication on the API server
• Disable token authentication to protect information in transit
• Disable Alpha APIs on the API server
• Enable ValidatingAdmissionWebhook
• Enable kernel protection in Kubelet
• Configure proper timeouts on Kubelet

Audit Configuration

Comprehensive audit logging is required for government clusters:

• Configure audit log path for the Kubernetes API Server
• Generate detailed audit records that capture event types, sources, results, users, and container associations
• Set appropriate audit log retention, size limits, and backup configurations

End User Workload Security

Workload security is equally important in government environments:

• Disable Kubernetes dashboard (unless explicitly required)
• Avoid using privileged host ports (below 1024) for user pods
• Never store secrets as environment variables (mount as volumes instead)
• Create and use dedicated namespaces for user-managed resources
• Implement Pod Security Standards to enforce baseline security controls

Implementing CIS Kubernetes Benchmark

The Center for Internet Security (CIS) Kubernetes Benchmark provides comprehensive security guidance for Kubernetes deployments:

1. Layered Security Approach:
   • Cluster-level security for physical infrastructure and configurable components
   • Node-level security for host machine configurations
   • Workload-level security for containers and applications
2. Security Levels:
   • Level 1: Basic security measures that don’t interfere with regular operations
   • Level 2: Advanced security measures for deeper protection that may affect functionality
3. Automated Compliance Verification:
   • Use kube-bench to automatically verify compliance with CIS Benchmarks
   • Integrate verification into CI/CD pipelines for continuous compliance

# Example: Running kube-bench to verify CIS compliance
docker run --pid=host -v /etc:/etc:ro -v /var:/var:ro -t aquasec/kube-bench:latest --version 1.18

Container Security for Government Environments

Container security is particularly critical in government settings, with specific requirements for hardening and validation.

Iron Bank and Container Hardening

The DoD’s Iron Bank provides hardened container images for government use:

1. Key Components:
   • Registry One: Fully compliant OCI registry with approved containers
   • Repo One: Central repository for hardened container source code
   • Vulnerability Assessment Tracker (VAT): Manages container justifications
   • Iron Bank Front End (IBFE): Web interface for container catalog access
2. Container Hardening Requirements:
   • Containers are rebuilt and rescanned every 12 hours
   • Images must comply with DoD security standards
   • All vulnerabilities must be documented and justified

NIST SP 800-190 Guidance

NIST’s Application Container Security Guide recommends specific practices:

1. Host OS Optimization:
   • Use container-specific host OSs with minimalist designs
   • Disable unnecessary services to reduce attack surfaces
   • Employ read-only file systems and other hardening practices
2. Container Isolation:
   • Run containers with the same purpose, sensitivity, and threat posture on a single host OS kernel
   • Implement proper isolation between containers and from the host OS

Network Security and Segmentation

Network security in government Kubernetes deployments follows specific patterns based on impact level requirements.

Network Security by Impact Level

Each impact level has specific network security requirements:

• IL4: Systems must operate within U.S. territories with NIPRNET connectivity
• IL5: Requires physical and logical separation of government data from non-government entities
• IL6: Mandates virtual/logical separation between DoD and federal tenants, with SIPRNet connectivity

Kubernetes Network Security

Within Kubernetes clusters, implement:

1. Service Mesh Implementation:
   • Mandatory for managing east-west traffic within the cluster
   • Enables mTLS between services
   • Enforces fine-grained access controls between microservices
2. Network Policies:
   • Define explicit ingress and egress rules for pods
   • Implement default-deny policies and allow only necessary traffic
   • Segment workloads by namespace with appropriate policies
3. Cloud Native Access Point (CNAP):
   • Implements zero-trust architecture for north-south traffic
   • Provides access to development, testing, and production enclaves at different impact levels

Access Control and Authentication

Authentication and access control requirements vary by impact level and must be properly implemented.

Authentication Requirements by Impact Level

• IL2: Standard authentication following FedRAMP Moderate
• IL4: Enhanced authentication with background checks for personnel
• IL5: Hardware token MFA (DoDI 8520.03 Credential Strength D) or PKI certificates, restricted to U.S. citizens
• IL6: Highest security authentication methods, limited to U.S. citizens with SECRET clearances

Role-Based Access Control (RBAC)

RBAC is essential in government Kubernetes deployments:

1. Principle of Least Privilege:
   • Define roles with minimal permissions required for functions
   • Create role bindings with appropriate scope (namespace or cluster)
   • Regularly audit permissions to identify overly permissive roles
2. Service Accounts:
   • Use dedicated service accounts for each application
   • Apply appropriate permissions to service accounts
   • Regularly rotate service account tokens

Secrets Management

Secure handling of secrets is critical in government Kubernetes environments.

Approved Solutions

HashiCorp Vault Enterprise stands out as a primary solution with FedRAMP compliance support:

1. Vault Integration Methods:
   • Vault Secrets Operator for native Kubernetes integration
   • vault-k8s sidecar for injecting secrets into pods
   • vault-csi-provider for mounting secrets as volumes
2. Key Management:
   • Implement automated key rotation
   • Use FIPS 140-2 compliant encryption algorithms
   • Implement proper access controls for key management

Best Practices

Follow DISA STIG requirements for secrets handling:

• Never store secrets as environment variables (always mount as volumes)
• Implement proper encryption of secrets at rest
• Establish audit logs for secrets access
• Use dedicated namespaces for secrets management

Policy Enforcement and Runtime Security

Policy enforcement ensures ongoing compliance with security requirements.

OPA Gatekeeper Implementation

Open Policy Agent (OPA) Gatekeeper enables enforcement of security policies:

1. Policy Implementation:
   • Define constraints for allowed/disallowed Kubernetes configurations
   • Create constraint templates for reusable policies
   • Implement audit and enforcement modes for policies
2. Common Policy Areas:
   • Repository restrictions for container images
   • Resource quota requirements
   • Label requirements for resources
   • Security context constraints

Google Policy Controller

For GKE environments, Policy Controller offers pre-built policy bundles:

1. Key Features:
   • Integration with Google Cloud
   • Pre-built policy bundles for security and compliance
   • Support for custom constraint templates
2. Policy Bundle Examples:
   • Pod Security Policy replacements
   • Cloud Service Mesh compliance
   • General security best practices

Continuous Monitoring and Vulnerability Management

Continuous monitoring is essential for maintaining security posture over time.

Vulnerability Scanning

Implement comprehensive vulnerability scanning:

1. Container Scanning:
   • Scan base images in CI/CD pipelines
   • Perform regular scans of running containers
   • Integrate with DoD vulnerability databases
2. Infrastructure Scanning:
   • Use tools like Checkov and Terrascan for IaC scanning
   • Implement kube-bench for ongoing compliance verification
   • Perform regular penetration testing

Continuous Monitoring

Establish monitoring systems for security events:

1. Security Monitoring:
   • Implement real-time monitoring of cluster activities
   • Configure alerting for potential security incidents
   • Integrate with security information and event management (SIEM) systems
2. Audit Logging:
   • Configure comprehensive audit logging per DISA STIG requirements
   • Establish appropriate retention policies
   • Implement secure log storage and analysis

Implementation Recommendations by Impact Level

The following sections provide specific implementation guidance for each impact level.

IL2 Implementation (Non-CUI Information)

For basic IL2 deployments:

1. Baseline Requirements:
   • Implement FedRAMP Moderate controls
   • Follow CIS Kubernetes Benchmark Level 1 recommendations
   • Use hardened container images from Iron Bank
2. Authentication:
   • Implement standard authentication methods
   • Apply basic RBAC configurations

IL4 Implementation (CUI Data)

For IL4 environments handling CUI:

1. Enhanced Security:
   • Implement FedRAMP High controls plus DoD-specific requirements
   • Follow CIS Kubernetes Benchmark Level 2 recommendations
   • Restrict access to U.S. Persons with appropriate background checks
2. Network Security:
   • Deploy within U.S. territories only
   • Implement NIPRNET connectivity
   • Apply comprehensive network policies

IL5 Implementation (Higher-Sensitivity CUI)

For IL5 environments with sensitive national security information:

1. Advanced Security:
   • Implement all IL4 controls plus additional IL5-specific requirements
   • Restrict access to U.S. citizens only
   • Require hardware token MFA or PKI certificates
2. Enhanced Segregation:
   • Implement physical and logical separation from non-federal entities
   • Apply strict pod security policies
   • Implement comprehensive audit logging

IL6 Implementation (Classified Information)

For IL6 environments with classified information:

1. Maximum Security:
   • Implement highest security controls
   • Restrict access to cleared personnel
   • Require SIPRNet connectivity
2. Classified Data Handling:
   • Apply strict data encryption requirements
   • Implement enhanced monitoring and alerting
   • Follow all classified information handling requirements

Wrapping It Up

Securing Kubernetes in government environments requires a comprehensive approach that addresses the unique requirements of DoD and federal systems. By following the specific guidance for each impact level and implementing the security controls outlined in DoD reference architectures, you can establish a secure foundation for container workloads in government settings.

The key to success is understanding the applicable impact level for your environment and implementing the corresponding security controls systematically. Regular assessment against DISA STIGs and CIS Benchmarks ensures ongoing compliance, while integration with approved tools and solutions helps maintain security posture over time.

As government security requirements evolve, staying current with DISA, NIST, and DoD guidance is essential for maintaining compliance and protecting sensitive information in Kubernetes environments.

Make sure you checkout the latest DoD DevSecOps available on the DISA website: https://public.cyber.mil/devsecops/

How AlphaBravo Can Accelerate Your Mission

At AlphaBravo, we specialize in securing Kubernetes clusters for government and defense organizations through our battle-tested ABOps platform and deep compliance expertise. Our approach integrates DISA STIG enforcement and Zero-Trust Architecture directly into your Kubernetes operations, ensuring your clusters meet DoD Impact Level 4 (IL4) and IL5 requirements out of the box. We deploy pre-hardened, Iron Bank-compliant containers and automate security controls like network policy enforcement and runtime vulnerability scanning, eliminating configuration drift while maintaining ATO readiness. Our platform will enforce NIST 800-53 and CNCF best practices across multi-cloud and air-gapped environments, providing consistent security whether you’re operating on AWS GovCloud, Azure Government, or disconnected tactical networks.

We solve unique government challenges through patented low-bandwidth GitOps synchronization and SBOM-driven artifact traceability – critical for environments with limited connectivity or strict software supply chain mandates. Our ABOps platform embeds security at every layer, from STIG-hardened host OS kernels to service mesh-enabled micro-segmentation that satisfies DoD’s zero-trust requirements. For classified workloads (IL6), we can implement NIPR/SIPR-compliant deployment patterns with FIPS 140-2 validated cryptographic modules and hardware-backed key management.

Our team brings operational experience from supporting DoD Platform One and PEO IWS Forge, translating policy into actionable controls. We pair our ABOps platform with hands-on Kubernetes Advanced Training that teaches your team to mitigate CVE-flagged containers and conduct NIST SP 800-190 compliant cluster audits. Whether you’re migrating legacy systems to Rancher Government Solutions or hardening vanilla Kubernetes for Mission Partner Environments (MPE), we provide the expertise and technology you need.