A number of cloud applications are currently widely used. However, one of the main reasons for the slowing down in the growth of cloud computing is that of security. Even though some research has been done in the security field, it is necessary to assess the current state of research and practice. This paper aims for the study of the existing research about security in cloud computing to analyze the state of art and to identify future directions. The method selected to investigate the security in cloud computing is a systematic mapping study. A total of 344 papers were selected and classified by security goal, research type and contribution type. The main security specific issues extracted are data protection (30.29%), access management (20.14%), software isolation (16.7%), availability (16%), trust (13.6%) and governance (3.27%). Our results demonstrate that cloud computing seems to be a promising area for security research and evaluation.