Which of the following is NOT a phase in the Software Development Lifecycle?

Deployment Testing is not a standard phase explicitly defined in the Software Development Lifecycle (SDLC). The SDLC typically comprises several well-defined stages such as requirements gathering, high-level design, detailed design, coding, testing, and maintenance.

While testing is certainly integral to the SDLC, it is usually categorized under phases like unit testing, integration testing, and system testing but doesn't specifically highlight "Deployment Testing" as a standalone phase. In many SDLC models, the deployment of software may include activities like installation and user training, yet it does not form a distinct phase named "Deployment Testing."

High-Level Design outlines the architecture of the software and its components, while Coding is the phase where the actual programming takes place. Security Threats is more of a consideration or factor that must be assessed and managed throughout the lifecycle rather than a phase in itself. Therefore, recognizing that Deployment Testing lacks the definition of an inherent phase in the SDLC is crucial in understanding the structure of software development processes.