Confidentiality is an important property that organizations relying on information technology have to preserve. The purpose of this work is to provide a structured approach for identifying confidentiality requirements. A key step in the information security risk management process is the determination of the impact level arisen from a loss of confidentiality, integrity or availability. We deal here with impact level determination regarding confidentiality by proposing a method to calculate impact levels based on the different kind of consequences typically arisen from threats. The proposed approach assesses the impact arisen from confidentiality losses on different areas separately and uses a parameterized model that allows organizations to adjust it according to their specific needs. A validation of the developed approach has been conducted in a small software development company.