With smarter plants comes a difficult challenge that has repercussions from the boardroom to manufacturing operations: ICS cybersecurity. This challenge has forged a new wave of innovative technologies. While industry has embraced these new technologies, which primarily take an IT-based approach to secure the perimeter of the control network, it has invested insufficiently in securing the systems directly responsible for plant processes and safety. In a growing threat landscape, insufficient control system security is no longer tenable. In this paper, we will discuss industry best practices for hardening OT/ICS cybersecurity, focusing on the first and most crucial step: inventory management.