Purpose: Operational technology (OT) environments face significant risks and threats stemming from Industry 4.0. The security landscape for OT is confronted with unprecedented challenges due to the expanding attack surface resulting from factors like cloud adoption, Industrial Internet of Things, and increased mobility. Securing OT networks has become increasingly complex, and relying solely on perimeter firewalls or air gaps is a flawed approach. Malicious actors now target OT systems for high-stakes ransoms and lockouts, exploiting the manufacturing industry's reluctance to disrupt operations. Conventional security measures are insufficient against insider threats and agile hackers who can maneuver within the network. These adversaries display patience and persistence, often waiting for months to gain unauthorized access. 

Acknowledging the complexity of OT within industrial organizations, the objective of this master's thesis is to offer a set of simplified principles and practices that can serve as valuable guidance for practitioners seeking to establish effective Attack Surface Management (ASM) strategies in OT environments. These OT security practices embody a comprehensive approach to cybersecurity, empowering OT security practitioners to adapt to ever-evolving industry dynamics and establish baseline protection against various threats and vulnerabilities.

Design/Methodology/Approach: This thesis utilizes Action Design Research (ADR), which combines Action Research (AR) and Design Science (DS) approaches. ADR is applied to address a specific problem in an organizational context, involving intervention, evaluation, and the creation of new IT principles and practices. ADR is chosen as the appropriate methodology to guide the development and evaluation of a prototype OT Remote Connectivity and the secure integration of MES components into the organizational OT environment.

Findings: This study made a valuable contribution to the field by introducing five innovative Design Principles (DPs) specifically designed to simplify ASM in OT environments. These newly proposed DPs complement the existing ones and address emerging challenges and considerations in the rapidly evolving landscape of OT security. They provide practitioners with fresh perspectives, guidelines, and approaches to enhance the effectiveness and efficiency of ASM strategies in OT.

Practical Implications: The research project gives a comprehensive checklist of secure practices for OT, these were formulated and implemented, considering the entire lifecycle of OT devices. These practices encompassed various stages, from design, procurement to disposal, and aimed to enhance the security posture of OT systems. Building upon these secure practices, a functional prototype was developed to facilitate secure remote connectivity for suppliers/vendors and the seamless integration of Manufacturing Execution System (MES) components.