Context: From the past few years, there has been a rapid progress in Cloud Computing. With the increasing number of companies resorting to use resources in the Cloud, there is a necessity for protecting the data of various users using centralized resources. Some major challenges that are being faced by Cloud Computing are to secure, protect and process the data which is the property of the user. Aims and Objectives: The main aim of this research is to understand the security threats and identify the appropriate security techniques used to mitigate them in Cloud Computing. The main objectives of this research are: • To understand the security issues and the techniques used in the current world of Cloud Computing. • To identify the security challenges, those are expected in the future of Cloud Computing. • To suggest counter measures for the future challenges to be faced in Cloud Computing. Research Methodology: In this study, we have used two research methods. • Systematic Literature Review. • Survey and interviews with various security experts working on Cloud Computing. Result: As a result, we have identified the total of 43 security challenges and 43 security techniques. The most measured attribute is confidentiality (31%) followed by integrity (24%) and availability (19%). The impact of identified mitigation techniques is mainly on security (30%), followed by performance (22%) and efficiency (17%). Also we have identified 17 future challenges and 8 mitigation practices. Conclusion: The identification of security challenges and mitigation techniques in large number of services of Cloud Computing is a very challenging task. In the process of identification from research methods (SLR and Survey), we had identified a satisfactory number of challenges and mitigation techniques which are being used at present and also in future Cloud Computing.