Who's in the Zone? A Qualitative Proof-of-Concept for Improving Remote Access Least-Privilege in ICS-SCADA Environments

Remote access control in many ICS-SCADA environments is of limited effectiveness leading to excessive privilege for staff who have responsibilities bounded by region, site, or device. Inability to implement more restrictive least-privilege access controls may result in unacceptable residual risk from internal and external threats. Security vendors and ICS cybersecurity practitioners have recognized this issue and provide options to address these concerns, such as inline security appliances, network authentication, and user-network based access control. Each of these solutions reduces privileges but has tradeoffs. This paper evaluates network-based access control combined with security zones and its benefits for existing ICS-SCADA environments. A Proof-of-Concept (PoC) evaluates a promising option that is not widely known or deployed in ICS-SCADA.