ADMS is the nerve center of modern electrical distribution networks, responsible for real-time monitoring, control, and optimization of power distribution. These systems rely heavily on interconnected devices, sensors, cloud services and software applications.

Security of the operational core: Measurement and control functions, associated with a SCADA subsystem, are at the critical core of an ADMS. The measurement and control operations are executed at (near) real time by sensors and actuators connected to ADMS through remote terminal units (RTUs), often via dedicated network connections. While the SCADA subsystems are traditionally secured by their physical isolation, in the context of an integrated ADMS special care needs to be taken to protect this critical part from tampering.

 
Cloud connectivity: Some key ADMS-related business processes extend outside the operational technology (OT) core of measurement and control. Network operation and state optimization requires diverse sources of information (relating, for example, to supply and consumption flexibility or weather) to be integrated to the central management capabilities of ADMS. On the other hand, ADMS often acts as a data source for external analytics capabilities. As these external systems are increasingly cloud-based, the ADMS attack surface extensions created by cloud connectivity need to be carefully managed.

Field work: Outage management processes, which form an essential part of an ADMS typically extend to the field and are often executed by diverse partner organizations specializing in field work. Efficient execution of field repairs requires the timely availability of network and fault-related information as well as the capability for remote updates of the work status. This is mostly accomplished with mobile applications, which need to be developed and deployed with focus on security.

 
Offline capabilities: Finally, it is typically required that as part of the OT for critical infrastructure, at least the core functionality of ADMS can stay operational in extreme circumstances, in many cases even without any external IP-based data connectivity. This means that the cyber security infrastructure needs to stay functional even without access to common cloud functionality, for example for encryption key management.
Cyber threats targeting ADMS can have severe consequences, ranging from service disruptions and data breaches to potential physical damage to critical infrastructure. As such, ensuring the security and integrity of ADMS is essential to maintaining the reliability and resilience of electrical grids.
 

Traditional cybersecurity approaches often rely on perimeter-based defenses. This means that the OT and IT networks are segmented into areas separated by firewalls and access controls, assuming that everything inside the network perimeter is trustworthy. This has been called the “verify, then trust” -approach. However, with the evolving threat landscape and the proliferation of insider threats and sophisticated external attacks, this model has proven inadequate. As discussed above, an ADMS brings together various IT and OT resources as well as diverse groups of users, including online and mobile. Even though the system can often be hardened by perimeter controls (for example around the core OT functions), they alone are clearly not sufficient.

The Zero Trust Model adopts a more proactive and comprehensive approach to cybersecurity. At its core, Zero Trust assumes that no entity, whether inside or outside the network, should be trusted by default. Instead, it requires continuous verification of identities, devices, and activities, regardless of their location or context. Zero Trust introduces a “never trust, always verify” mindset.

In an influential publication1 NIST provides an operative definition for a Zero Trust Architecture:

“Zero trust (ZT) provides a collection of concepts and ideas designed to minimize uncertainty in enforcing accurate, least privilege per-request access decisions in information systems and services in the face of a network viewed as compromised. Zero trust architecture (ZTA) is an enterprise’s cybersecurity plan that utilizes zero trust concepts and encompasses component relationships, workflow planning, and access policies. Therefore, a zero trust enterprise is the network infrastructure (physical and virtual) and operational policies that are in place for an enterprise as a product of a zero trust architecture plan.”

Creating a Zero Trust Architecture for an ADMS deployment should include consideration of at least the following key principles and practices:

Identity-Centric Security: Identity is the new perimeter in a Zero Trust environment. Access to ADMS resources is based on strict identity verification, including multi-factor authentication and least privilege access controls. No shared accounts are used and granular role-based access control (RBAC) rules are in use, also for the field applications.

Micro-Segmentation refers to the division of a network into isolated, separately accessed sections with their own security policies and access controls to prevent lateral spreading of cybersecurity threats. A system architecture based on microservices offers a natural basis for encapsulating and securing the core ADMS functions. Specifically, access to any operationally critical measurement and control -related services must be strictly controlled. 

Service authentication and authorization: In addition to users, the resource access by any system services is controlled by strict security policies, including service-level authentication and authorization. This requires a carefully orchestrated service architecture.

Continuous Monitoring and Analytics: Real-time monitoring of user and device activities allows for early detection of suspicious behavior or anomalies. Advanced analytics and machine learning algorithms help identify and respond to potential threats more effectively.

Encryption and Data Protection: All data transmitted within the ADMS environment, whether at rest or in transit, is encrypted to prevent unauthorized access or tampering. Encryption key management is centralized and secured. 

Endpoint Security: Endpoints such as workstations, servers, and IoT devices are hardened with robust security measures, including regular patching, endpoint detection and response (EDR) solutions, and application whitelisting. In case of on-premise deployment, physical access to the system endpoints is restricted, especially for the OT subsystems. 

¹Rose, S. , Borchert, O. , Mitchell, S. and Connelly, S. (2020), Zero Trust Architecture, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.SP.800-207, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=930420 (Accessed February 26, 2024)