Open source software (OSS) allows users and developers to, amongst others, study, modify and redistribute the source code. At the other end of the spectrum, closed source software (CSS -the antonym of OSS) disallows users and developers to access and modify any source code. This paper presents an overview of security challenges during closed source systems (CSS) to open source systems (OSS) migrations and proposes a Model to address such challenges. A comparison of OSS security and CSS security aspects, and an overview of security challenges during migrations to OSS are presented. On the strength of these comparisons, and using summative content analysis, a model to address security challenges during migrations to OSS is proposed. The model is developed through enhancements of previous models aimed at addressing security threats and protecting sensitive information during system migrations. The 9th International Conference for Internet Technology and Secured Transactions (ICITST-2014) 978-1-908320-39/1/$25.00©2014 IEEE 274 The 9th International Conference for Internet Technology and Secured Transactions (ICITST-2014) 978-1-908320-39/1/$25.00©2014 IEEE 275 The 9th International Conference for Internet Technology and Secured Transactions (ICITST-2014) 978-1-908320-39/1/$25.00©2014 IEEE 282 The 9th International Conference for Internet Technology and Secured Transactions (ICITST-2014) 978-1-908320-39/1/$25.00©2014 IEEE