Software security breaches are now very extremely common and a larger percentage is caused by software design defects. Since individuals and organizations now completely depend on software systems for their day-to-day operations, it is then important to produce secure software products. This paper discusses the problems of producing secure software products and provides a model for improving software security. The model - Secure Software Development Model (SSDM), is unified model that integrates security engineering with software engineering so as to ensure effective production of secure software products. Supporting structure in form of laws is also presented to guide developers throughout the development process. We then present our experience that validates the model.