This article proposes a method to help students develop a security mindset by incorporating security concepts into a university-level introductory programming course. The method is based on a mapping of introductory programming topics to relevant security concepts. The mapping is used to modify lecture materials and programming projects to incorporate security-related information and requirements. These modifications are added gradually, with minimal impact on existing learning outcomes and expected student effort. We evaluated our method in a case study on the introduction of security concepts in an introductory programming course in Python. For this, we analyzed student programming projects and conducted a post-course survey. The results show improved security implementation in student projects and increased awareness of the importance of security in programming.