Explanation
The best time during the secure development life cycle to perform privacy threat modeling is early in the design phase, because this will help identify and mitigate the potential privacy risks and vulnerabilities of the system or application before they become costly or difficult to fix. Privacy threat modeling is a systematic process of analyzing the data flows, assets, actors, and scenarios of a system or application to identify and prioritize the privacy threats and countermeasures12. Performing privacy threat modeling early in the design phase will also help ensure that privacy is built into the system or application from the start, rather than as an afterthought.
References:
* CDPSE Exam Content Outline, Domain 2 - Privacy Architecture (Privacy Architecture Implementation), Task 2: Implement privacy solutions3.
* CDPSE Review Manual, Chapter 2 - Privacy Architecture, Section 2.3 - Privacy Architecture Implementation4.