What is the Definition and Importance of Critical Infrastructures?

Critical infrastructures are indispensable elements for the functioning of modern societies. These infrastructures, which ensure the continuity of essential services such as energy production, water supply, transportation, communication, and finance, are also an integral part of national security. While cyber threats have dominated discussions in recent years, the physical security aspect is often neglected or treated as secondary. However, physical attacks can have more immediate, more destructive, and often irreversible consequences (Berg & Tatham, 2021).

In this context, this study examines the factors that threaten the physical security of critical infrastructures, the security measures that need to be implemented, national and international regulations, and future technology-based approaches. According to the European Commission, a critical infrastructure is defined as “any system, resource, or asset that could cause significant damage to the functioning of society” (European Commission, 2006).

In Turkey, this definition is further elaborated in national strategy documents published by the Information and Communication Technologies Authority (BTK) and the Presidential Digital Transformation Office.

Critical infrastructures are generally classified under the following categories: energy infrastructure, transportation infrastructure, communication infrastructure, water and sewage infrastructure, financial system infrastructure, and healthcare infrastructure.

The failure of any of these infrastructures can create a cascading effect, threatening the overall security of society (Rinaldi, Peerenboom & Kelly, 2001)

Classification of Physical Security Threats and Their Role in Corporate Risk Management

Physical security encompasses all measures taken to protect a corporation’s infrastructure, personnel, and equipment. Proper classification and analysis of physical threats are critical to the effectiveness of risk management processes. These threats can generally be categorized into two main groups: internal and external threats.

Intentional actions that threaten the physical integrity of an organization can be executed by both internal and external actors. Among external threats, sabotage, vandalism, theft, and unauthorized access are prominent, while internal threats usually stem from deliberate violations by the organization’s personnel. These threats can cause not only physical damage but also disruptions to operational processes. Particularly in organizations with strategic infrastructure, these risks must be carefully managed through preventive security protocols.
Natural disasters are unforeseen and uncontrollable events that pose significant physical security threats. Events such as earthquakes, floods, storms, and lightning can lead to structural damage and service interruptions. To mitigate the impact of such disasters, it is crucial to construct buildings with disaster-resistant designs and develop comprehensive emergency plans. Additionally, conducting environmental risk assessments in areas housing critical assets contributes to long-term security strategies.

Physical security requires protection not only against external threats but also against internal disruptions. Technical issues such as power outages, equipment failures, and malfunctioning fire systems, along with human errors, are also considered within this scope. These risks often arise due to maintenance deficiencies, inadequate training, or lack of procedures. Preventive maintenance programs, regular inspections, and continuous training for staff are essential tools for minimizing the impact of these threats.

In conclusion, effectively managing physical security threats plays a fundamental role in ensuring corporate continuity and operational security. Whether intentional attacks, natural events, or technical failures, all can potentially cause significant disruptions to an organization’s operations. Therefore, risks related to physical security should be addressed with a holistic approach under the responsibility of not just security units but all levels of organizational management.

Physical Security Measures for Critical Infrastructures: The Multi-Layered Security Approach

Physical security is not something that can be achieved solely with specific devices. An effective security strategy requires adopting a multi-layered approach. Layered security is an integrated defense system that extends from the external environment to the interior. This method increases the security level by providing protection against different threats at each stage (Garcia, 2008). The layered security concept allows various security measures to work together, offering different threat detection and prevention strategies at each layer.
External Security / Protection Perimeter & Layer: The first line of defense in physical security measures is the outer layer. This layer ensures the protection of organizations against threats from the external environment. The main components include:
•    Physical Barriers: Fences, walls, and other barriers prevent unauthorized access from the outside. These structures serve as the first line of defense against external threats.
•    Lighting Systems: Adequate outdoor lighting makes it more difficult for criminals to hide, thus enhancing security.
•    Security Cameras (CCTV): Visual monitoring helps detect potential threats, making it easier to identify them.
•    Security Guards and Patrol Systems: Physical patrolling and human surveillance help manage threats that automated systems may not detect.

Middle Security / Protection Perimeter & Layer: This layer involves more detailed security measures to control the transition from the outer layer to the interior. The security technologies used in this layer include:
•    Access Control Systems: Card-based access systems and biometric verification ensure that only authorized individuals can enter specific areas.
•    X-Ray Machines and Metal Detectors: These systems help detect dangerous items carried by visitors and staff.
•    Visitor Control Protocols: The process of verifying visitors' identities prevents unauthorized individuals from entering the premises.

Internal Security / Protection Perimeter & Layer: This layer focuses on the protection of critical areas and offers more specific security measures against internal threats. The elements used in this layer include:
•    Locked Compartments: Critical areas are protected with locked compartments, granting access only to authorized personnel.
•    Motion and Temperature Sensors: These sensors monitor movement and temperature fluctuations within the premises, enabling an immediate response to potential threats.
•    Alarm Systems: In the event of a security breach, alarm systems activate to alert authorized personnel.
•    Access Limitations: Access restrictions for employees ensure that they only enter areas for which they are authorized, protecting against internal threats.

This multi-layered security approach provides comprehensive protection by addressing external and internal threats through various integrated security measures.

What Are the International Regulations and Standards for Critical Infrastructure Security?

Physical security practices are shaped not only by internal policies but also by national and international regulations and standards. These regulations are of great importance to ensure that security measures comply with internationally recognized norms and provide effective protection against the threats organizations may face. Below, some prominent standards and legal frameworks related to physical security are examined.

Information Security Management System ISO/IEC 27001: This is a globally recognized standard for an organization’s information security management system (ISMS). The standard establishes procedures for managing various risks in the information security field while also providing additional requirements for physical and environmental security. In particular, in data centers and critical infrastructures, it emphasizes the need to align physical security measures with the standard to ensure information security. ISO/IEC 27001 allows organizations to systematically integrate all aspects of their security strategies.

Cyber-Physical Security Guide for Industrial Control Systems NIST SP 800-82: Published by the U.S. National Institute of Standards and Technology (NIST), SP 800-82 is one of the most significant guides in the field of cyber-physical security for industrial control systems (ICS). This standard focuses on the security of infrastructures in critical sectors such as energy, water, and transportation. It provides guidance on integrating physical security measures with cybersecurity measures and manages the interaction between both areas. This approach aims to enhance the security of industrial systems while minimizing operational disruptions.

Critical Infrastructure Protection Standards for Energy Infrastructures in North America NERC CIP: The Critical Infrastructure Protection (CIP) standards published by the North American Electric Reliability Corporation (NERC) apply to all organizations operating in the energy sector. These standards cover physical security measures, access control systems, and emergency response plans to ensure the security of energy infrastructures. NERC CIP protects critical systems in the energy sector from targeted threats and ensures the continuous operability of these systems.

Compliance with these standards offers strategic advantages, not only as a legal obligation but also in terms of corporate reputation and operational continuity