Which phase of the software development life cycle includes determining business and security requirements?

The phase of the software development life cycle that involves determining business and security requirements is the defining phase. During this stage, stakeholders come together to gather and clarify the goals of the project, which includes understanding both the functional aspects necessary for the business as well as the security requirements that must be met to protect data and ensure compliance with regulations.

Identifying security requirements early in the development process is crucial because it allows for the integration of security measures into the design and architecture of the software. This proactive approach helps to mitigate risks and ensures that security considerations are not an afterthought, which can lead to vulnerabilities and costly fixes later on.

In contrast, the designing phase is more focused on how to implement the requirements identified in the defining phase, while the developing phase involves coding and building the software. The testing phase is where the software is evaluated for defects and adherence to requirements but does not focus on gathering and establishing those initial requirements.