As a consequence to factors such as progress made by the attackers, release of new technologies and use of increasingly complex systems, and threats to applications security have been continuously evolving. Security of code and privacy of data must be implemented in both design and programming practice to face such scenarios. In such a context, this paper proposes a software development approach, Privacy Oriented Software Development (POSD), that complements traditional development processes by integrating the activities needed for addressing security and privacy management in software systems. The approach is based on 5 key elements (Privacy by Design, Privacy Design Strategies, Privacy Pattern, Vulnerabilities, Context). The approach can be applied in two directions forward and backward, for developing new software systems or re-engineering an existing one. This paper presents the POSD approach in the backward mode together with an application in the context of an industrial project. Results show that POSD is able to discover software vulnerabilities, identify the remediation patterns needed for addressing them in the source code, and design the target architecture to be used for guiding privacy-oriented system re-engineering.