Introduction
Air-gapped networks cannot call out to Active Directory or a cloud identity provider, so how do you verify that the person plugging a USB into a SCADA workstation is who they claim to be? Managing user identity and access control in air-gapped environments is one of the hardest problems in OT security. This article covers the practical approaches that work without network connectivity, from hardware tokens to local authentication servers, while meeting NIST 800-171, CMMC, and NIS2 requirements.
Understanding Air-Gapped Environments
What Is an Air-Gapped Environment?
An air-gapped environment is a network that is physically isolated from unsecured networks, particularly the internet. This isolation is designed to protect sensitive data and critical systems from cyber threats. Air-gapped systems are often used in defense, industrial control systems (ICS), and other critical infrastructure sectors.
Importance of Air-Gapping in OT Security
In Operational Technology (OT), air-gapping is employed to safeguard critical infrastructure against cyber threats. By isolating these systems, organizations aim to prevent unauthorized access and maintain the integrity and availability of essential services. However, despite the isolation, air-gapped systems are not immune to security breaches (as Stuxnet demonstrated), reinforcing the need for strong access control measures.
Challenges of User Identity and Access Control in Air-Gapped Environments
Limited Connectivity
The primary challenge in air-gapped environments is the lack of direct connectivity, which complicates the implementation of centralized identity management systems. Without connectivity to the broader network, traditional methods of user authentication and access control become less effective.
Authentication Complexity
Implementing multi-factor authentication (MFA) in air-gapped environments can be challenging due to the limited availability of external authentication services. This necessitates the use of on-premise authentication solutions that do not depend on external networks.
User Identity Verification
Ensuring that the identity of users accessing the air-gapped environment is genuine and verified is critical. This requires identity verification processes that can operate independently of external identity providers.
Strategies for Managing User Identity and Access Control
On-Premise Identity Management Solutions
Investing in an on-premise identity management solution that supports the unique requirements of air-gapped environments is essential. These solutions should provide:
- Local authentication servers that can operate without internet connectivity.
- Role-based access controls to restrict user access based on their job functions.
- Audit trails to track and log user activities for compliance and security monitoring.
Implementing Strong Authentication Methods
While implementing MFA can be challenging in air-gapped systems, it remains a critical component of security. Consider the following approaches:
- Hardware tokens or smart cards that do not require network connectivity.
- Biometric authentication methods that can be implemented locally.
- Time-based one-time passwords (TOTP) that can be generated offline.
Physical Security Measures
Physical security plays a significant role in protecting air-gapped environments. Consider implementing:
- Badge access systems to control physical entry to sensitive areas.
- Surveillance systems to monitor and record access to critical infrastructure.
- Restricted physical access to network components, ensuring only authorized personnel have direct interaction with the systems.
Compliance Considerations
Aligning with NIST 800-171
For organizations handling Controlled Unclassified Information (CUI), compliance with NIST 800-171 is mandatory. Key requirements include:
- Implementing access control measures to ensure authorized access.
- Ensuring user identity verification processes are robust and compliant.
- Maintaining audit logs for monitoring and reporting purposes.
CMMC Compliance
The Cybersecurity Maturity Model Certification (CMMC) mandates various levels of cybersecurity hygiene. To achieve compliance:
- Implement identity and access management (IAM) practices that meet CMMC Level 3 requirements.
- Ensure that user access is reviewed regularly and unnecessary privileges are revoked promptly.
NIS2 Directive
The NIS2 directive requires organizations to strengthen their cybersecurity measures across the EU. For air-gapped environments, this entails:
- Enforcing stringent access control measures.
- Ensuring that identity verification processes align with the directive’s requirements.
- Regularly auditing and updating security measures to address emerging threats.
Best Practices for Enhancing Security
Regular Security Audits
Conduct regular security audits to identify and rectify vulnerabilities in the access control systems. This includes reviewing user access logs and ensuring all access points are secure.
Training and Awareness
Provide regular training and awareness programs for personnel to ensure they understand the importance of access control and the procedures in place. This helps maintain a security-conscious culture within the organization.
Incident Response Planning
Develop and maintain an incident response plan specifically tailored for air-gapped environments. This plan should outline procedures for detecting and responding to security incidents, ensuring minimal impact on operations.
Conclusion
Start by deploying a local authentication server with hardware token support, enforce role-based access for every air-gapped workstation, and audit access logs monthly. Air-gapped does not mean risk-free, and identity management is the control that closes the gap.
