###### Abstract  
The increased connectivity and automation capabilities of Industry 4.0 cyber-physical production systems (CPPS) create significant cyber-security vulnerabilities in supervisory control and data acquisition (SCADA) environments if robust protections are not properly implemented. Legacy industrial control systems and new IP-enabled sensors, instruments, controllers, and appliances often lack basic safeguards like encryption, rigorous access controls, and endpoint security. This exposes manufacturers to substantial risks of cyberattacks that could manipulate, disrupt, or disable critical physical assets and processes related to their production lines and facilities. This study presents a multilayered cybersecurity framework to address these challenges and harden SCADA environments by implementing granular access controls, network micro-segmentation, anomaly detection, encrypted communications, and legacy system upgrades. The multilayered defense-in-depth (DID) approach combines policies, processes, and technologies to counter emerging vulnerabilities. The methodology was implemented in an electronics manufacturing facility across access control, zooming, monitoring, and encryption scenarios. Results show security improvements, including 57.4% fewer unauthorized access events, 41.2% faster threat containment, and 79.2% fewer hacking attempts. The quantified metrics highlight the CPPS resilience and threat mitigation capabilities enabled by the securely designed SCADA architecture, which allows manufacturers to confidently pursue Industry 4.0 integration and digital transformation with minimized disruption. SCADA security; secure CPPS; Industry 4.0; multilayered DID +
Footnote †: journal: Applied sciences  
introduces cybersecurity risks that manufacturers need to manage proactively to avoid undermining operational resilience and safety [4]. In the electronics manufacturing field, attackers gaining access through corporate IT networks could penetrate and hijack SCADA systems on the factory floor to disrupt or shut down production lines, manipulate bill of material (BoM) databases to introduce counterfeit components, steal sensitive intellectual property like proprietary design schematics, or intentionally damage manufacturing equipment [4]. Most legacy industrial control devices and systems, including programmable logic controllers (PLC), sensor arrays, automation appliances, and single-purpose embedded devices, were designed without cybersecurity considerations in mind and, hence, incorporate few protections beyond simple passwords or limited access controls [5]. For example, SCADA networks traditionally relied on isolation from external networks and proprietary protocols rather than using rigorous authentication or encryption to secure systems. Consequently, the new attack pathways created by increasing interconnectivity between traditionally isolated OT systems and corporate IT systems require multilayered defenses across policies, processes, and technologies encompassing the full environment. The objectives of this study are to propose and validate a multilayered cybersecurity framework encompassing access controls, network segmentation, encrypted communications, anomaly detection, and legacy upgrades to secure SCADA systems and enable electronics manufacturers to safely pursue Industry 4.0 integration. At the organizational policy level, cybersecurity best practices are defined for critical procedures like user access management, patch management, vulnerability scanning, backup and recovery, and incident response [6]. Strategic and tactical policies are set to guide security across environments. At the process layer, protection technologies like firewalls, intrusion detection systems, and role-based access controls are required to align with defined policies to provide concrete safeguards [7]. Firewalls, multifactor authentication, and network monitoring provide technical enforcement for policies.