A mature organization with legacy information systems has incorporated numerous new processes and dependencies to manage security as its networks and infrastructure are modernized. The Chief…

Agile development is defined by short iterative cycles, frequent software releases, and continuous collaboration with business stakeholders and end users to capture and incorporate evolving requirements. The scenario explicitly describes frequent vendor releases and constant vendor communication with personnel to understand business processes and gather new requirements, which are hallmark characteristics of Agile. The CIO's frustration with the release frequency further confirms an Agile cadence rather than a single large delivery model.

SDL (Security Development Lifecycle) is a security practice framework integrated into a development process and is not a methodology defined by release cadence or iterative stakeholder requirement gathering.

Waterfall is a sequential, phase-gated methodology where all requirements are captured upfront before development begins, making frequent releases and ongoing requirement gathering from users inconsistent with its structure.

Joint Application Development (JAD) is a structured facilitated workshop technique for gathering requirements collaboratively, not a full iterative development methodology characterized by frequent production releases.