Secure remote access for Controlled Unclassified Information (CUI) is a critical compliance requirement under the Compliance Framework (NIST SP 800-171 Rev.2 / CMMC 2.0 Level 2 - PE.L2-3.10.6): it requires organizations to control, authenticate, monitor, and protect remote connections so that CUI is not exposed via insecure endpoints or weak authentication.
Key objectives and planning
The primary objectives are straightforward: authenticate users and devices strongly before granting access, limit access to the minimum resources required (least privilege), encrypt communications end-to-end, monitor and log sessions for audit, and maintain policies and evidence to demonstrate compliance. For a small business this begins with an accurate asset inventory (who, what device, where the CUI lives), a documented remote access policy, and a simple risk assessment that focuses on remote users and third-party contractors.
Technical controls — step-by-step implementation
Start by choosing the right remote access architecture for your environment: either a VPN with robust controls or a Zero Trust Network Access (ZTNA) solution. For VPNs, use modern protocols only (IKEv2/IPsec, OpenVPN with TLS 1.2+/TLS 1.3, or WireGuard) and disable legacy protocols (PPTP, L2TP without IPsec). Enforce strong cryptography (TLS 1.2+ with AES-GCM or ChaCha20-Poly1305, certificate validation, no static keys). If you select ZTNA (Cloudflare Access, Google BeyondCorp, Okta, Zscaler), require device posture checks and application-level access instead of network-level access.
Implement multifactor authentication (MFA) for all remote access. Practical options: integrate your identity provider (Azure AD, Okta, Google Workspace) and require MFA via FIDO2 hardware tokens (YubiKey) for privileged users and TOTP or push-based MFA (Duo, Microsoft Authenticator) for others. For administrative or contractor access, elevate assurance by requiring hardware-backed MFA and use short session lifetimes. Where possible, implement mutual TLS or certificate-based device authentication (managed via your PKI or MDM) in addition to user MFA.
Endpoint and session protections
Ensure every remote device meets minimum posture checks before access is granted: disk encryption (BitLocker/FileVault), up-to-date OS patches, an approved EDR/antivirus agent, screen lock, and disabled insecure services. Use Mobile Device Management (MDM) or Endpoint Management tools (Intune, Jamf, SentinelOne) to enforce configuration. Prevent split-tunneling to avoid bypassing corporate controls, or use Conditional Access policies to restrict which apps/data can be accessed based on device posture and location. For sensitive administrative sessions, route access through a bastion (jump) host with session recording and command logging (SSH session recording, RDP recording) to meet audit requirements.
Logging, monitoring, and evidence collection
Centralize logs from VPNs/ZTNA, identity providers, bastion hosts, and endpoints to a log collector or SIEM (Splunk, ELK, Azure Sentinel). Record authentication events, VPN/ZTNA session start/stop, IP addresses, device identifiers, and privileged command execution. Retain logs for the period required by your compliance program (30–365 days depending on contractual requirements) and create an evidence folder for assessors: remote access policy, configuration snapshots (VPN server configs, ZTNA application policies), MFA enrollment reports, and sample logs showing successful and blocked connections.
Practical small-business scenarios
Scenario A — Small engineering firm with remote designers: They host CUI CAD files in a cloud file share. Implement a cloud ZTNA that only allows access to the file share URL and requires device compliance (disk encryption + EDR). Use SSO with Azure AD and enforce MFA. Disable sync for personal devices and require company-managed endpoints for CUI access. Maintain one master log stream and monthly access reviews to disable stale accounts.
Scenario B — Manufacturer with remote machinists and external contractors: The manufacturer uses a VPN for legacy shop floor systems. Replace legacy VPN endpoints with a modern VPN appliance (or ZTNA if feasible), enforce certificate-based device authentication, and require contractors to sign a remote access agreement that mandates MFA and limits hours of access. Route contractor sessions through a bastion host with session recording and collect session artifacts for audits. Example low-cost solutions: OpenVPN Access Server with RADIUS + Duo, or Cloudflare Access with GitHub/Okta SSO for contractors.
Compliance tips, common pitfalls, and evidence for assessors
Compliance tips: 1) Document policies and procedures for remote access, including onboarding/offboarding and contractor agreements. 2) Map controls to NIST SP 800-171/CMMC artifacts: policy documents, configurations, logs, and training records. 3) Automate evidence collection where possible (daily exports of authentication logs, system configuration snapshots). Common pitfalls: allowing split tunneling, not requiring device management for BYOD, relying solely on passwords, and failing to log and retain session data. For assessments, provide: network diagrams showing segmentation, VPN/ ZTNA config files, MFA enrollment reports, sample session logs, and change-control tickets for any remote-access appliances.
Risk of not implementing secure remote access
Failure to secure remote access increases the risk of credential theft, lateral movement into networks that store CUI, and exfiltration of sensitive data. Consequences include loss of DoD contracts, remediation costs, regulatory findings, and reputational harm. For small businesses, a single compromised remote credential can lead to months of downtime and expensive incident response — often far costlier than implementing the controls described above.
In summary, achieving Compliance Framework alignment for PE.L2-3.10.6 requires a combination of policy, modern authentication (MFA + certificates), device posture enforcement, secure transport (VPN or ZTNA), centralized logging, and demonstrable evidence. Start with inventory and policy, choose defensible technical controls appropriate to your budget (cloud ZTNA or modern VPN + bastion host), enforce endpoint security, and build an evidence collection routine so you can prove compliance to an assessor. With these practical steps, small businesses can secure remote access to CUI without excessive complexity.
