Modern petrochemical plants depend on industrial control systems for safe and efficient operation. As these systems become more connected and integrated with IT networks, cybersecurity has evolved from an IT concern into a core engineering discipline. This article examines the cybersecurity challenges facing DCS and SCADA systems in petrochemical environments, explains the IEC 62443 framework and zone-conduit model, and provides practical engineering guidance for network segmentation, device hardening, patch management, and incident response.