# Secure Cloud Infrastructure: A Survey on Issues, Current Solutions, and Open Challenges
## 3 Cloud Computing Background and Terminologies
### Existing Surveys
It also contributed to the identification of a unified taxonomy for security requirements, threats, vulnerabilities, and countermeasures for end-to-end mapping. It also highlighted security challenges in other related fields, such as trust-based security models, cloud-enabled big data applications, the Internet of Things (IoT), the software defined network (SDN), and network function virtualization (NFV). The study in [29] conducted a systematic literature review of the integration as a service between trusted computing and cloud computing for infrastructure as a service (IaaS). Cloud computing integration and trusted computing can create a new infrastructure architecture as a service that encourages more cloud service tenants to trust cloud service providers. A survey in [17] provided security issues and requirements for the cloud and identified threats and known vulnerabilities. The work presented a new classification of recent security solutions that exist in this area. It presented a series of documented policies, procedures and processes that define a secure way to manage the cloud environment to identify the vulnerability and increase confidence in an ever-connected world. In [30], the authors investigated the key contemporary security problem in cloud computing and provided the best practices for service providers and organizations hoping to manage cloud services. Table 2 presents a summary of the existing related surveys in terms of their contributions and the levels of infrastructure they covered. It summarizes existing survey papers in cloud infrastructure over the period from 2016 to 2020. As noticed, most of these surveys were conducted at only one level of cloud infrastructure. For instance, the surveys in [19; 20; 23; 28], focused on only the data level, while the survey in [24] focused on only the application level. Moreover, a survey [26] was conducted on the network level and another paper [30] on the host level. There have been some works performed at two or more levels in cloud infrastructure, such as the studies conducted in [18; 22; 25]. In addition, the studies in [21; 27; 29; 31], considered all infrastructure levels. Nevertheless, [20] considered a public cloud only, and also for cloud services in terms of cloud infrastructure vendors and revenue. Meanwhile the survey in [27] focused more on how to manage the data in the public cloud. The study in [29] was a narrative review without any analyses of the reviewed materials. Lastly, the survey in [31] was limited to the analyses of security from the provider's perspective. To conclude, the existing survey papers in cloud infrastructure security are not comprehensive enough. They do not cover the security of all levels of cloud infrastructure, i.e., host, network, application and data. Some of the reported surveys are limited to one or more levels. In addition, some surveys do not consider all perspectives of customers and service providers. Our proposed survey is different, such that it conducts an extensive review of issues that faced all levels of cloud computing infrastructure with a proper analysis of such issues. Then, it discusses the existing solutions used to mitigate these issues. Finally, the survey highlights the open issues and challenges, and gives directions for future research.