Ola is a research associate at the University of Bristol and is interested in the 'making of' technology, science and policy, specifically about the Cybersecurity of Critical National InfrastructuresFacilities like power plants, water pipes and railway stations underpin contemporary living standards across the world. For decades, they have been operated by Operational Technologies (OT), basic (yet sturdy!) computers without Internet access. People working in OT facilities are traditionally manual workers or engineers with training in safety.In this session, Ola presents the results of a qualitative study conducted between November 2019-January 2020, where her and her team interviewed 30 UK-based security practitioners with expertise in critical infrastructures. Their analysis is concerned with the following questions: How do security practitioners define (in)security? How do they evidence it? What capabilities make a good OT security worker?