Which role is primarily responsible for maintaining system security throughout its lifecycle?

The role that is primarily responsible for maintaining system security throughout its lifecycle is the System Owner. This individual is tasked with a comprehensive understanding and oversight of the system's security requirements from its inception to its decommissioning. The System Owner is in charge of ensuring that the system complies with security policies and regulations, manages risks associated with the system, and implements necessary security controls and updates to protect it against vulnerabilities.

Throughout the lifecycle, the System Owner works closely with various stakeholders to ensure that the security posture of the system is continuously evaluated and improved as necessary. This includes planning for security in the design phase, implementing controls during the operational phase, and managing any changes or risks that may emerge over time. The System Owner is therefore central in creating a secure environment that aligns with organizational policies and standards, as well as in responding to any threats that may arise post-implementation.