APTA SS-TCS-WP-002-26

This white paper examines the foundational role of visibility in securing modern rail transit systems. It focuses on the comprehensive identification and documentation of assets, networks and systems, which forms the bedrock of effective risk management and cybersecurity in increasingly digitalized transit environments. This document is a proactive effort to ensure that rail agencies can fully understand their operational landscapes and make informed decisions to protect them. It explores the importance of maintaining accurate and dynamic asset inventories, understanding data flows across the transit environment, and ensuring secure interfaces between IT and OT networks. By aligning these practices with the NIST Cybersecurity Framework and APTA’s OT-Cybersecurity Maturity Framework (OT-CMF), it provides practical guidance for integrating visibility into the day-to-day operations of transit agencies. This paper also highlights the importance of implementing robust governance structures and continuous improvement practices. Recommendations are offered for building or refining visibility initiatives, including best practices for leveraging standards, engaging vendors and conducting periodic reviews to stay ahead of emerging threats. Visibility is not just a security function but an operational imperative. By prioritizing visibility, rail transit agencies can create the foundation for a more resilient, adaptable and secure future.