I. Introduction  
II. Railways as an Integrated System  
A. The Dualism Between Safety and Security  
B. Security Landscape in the Railway Industry  
C. A Deeper Look at Signaling Systems  
D. Security Aspects of ERTMS  
E. The Limits of an Atomistic Approach  
III. Security Assessment Methodologies for Railway Systems  
A. Standards for Cybersecurity Assessments  
B. Guidelines to Enhance the Security of Railway Systems  
C. The Issue of Safety Certification  
IV. An Enterprise-Oriented Approach to Security Risk Management  
V. Cyber Ranges as Assessment Tools  
A. The Landscape of Cyber Ranges  
B. The Role of Cyber Ranges for Network Security  
VI. Future Challenges and Conclusions