###### Abstract  
Cloud computing (CC) plays a significant role in revolutionizing the information and communication technology (ICT) industry, allowing flexible delivery of new services and computing resources at a fraction of the costs for end-users than traditional computing. Unfortunately, many potential cyber threats impact CC-deployed services due to the exploitation of CC's characteristics, such as resource sharing, elasticity, and multi-tenancy. This survey provides a comprehensive discussion on security issues and challenges facing CC for cloud service providers and their users. Furthermore, this survey proposes a new taxonomy for classifying CC attacks, distributed denial of service (DDoS) attacks, and DDoS attack detection approaches on CC. It also provides a qualitative comparison with the existing surveys. Finally, this survey aims to serve as a guide and reference for other researchers working on new DDoS attack detection approaches within the CC environment. cyber-threats; cloud computing (CC); cloud security; distributed denial of service (DDoS) attacks; cybersecurity +
Footnote †: journal: Applied  
Internet usage has increased by 50% in several European countries and 30% in the United Kingdom, reflecting the growth in the ICT sector spurred by surges in demands for online-based utilities and services. As a result, more issues and threats with CC will surface in due time, such as security and privacy breaches, data storage issues in the CC, and application-layer attacks [7,8]. Nowadays, major attacks on CC are growing, and the effects on its security are becoming more apparent. For example, attacks include malicious attempts by adversaries to deny legitimate users from obtaining services offered by the targeted servers [9]. Cloud service providers (CSP) charge their clients based on the services rendered or resources utilized on a pay-per-use basis. A new form of DDoS attack, called Economic denial of sustainability (EDoS), manipulates the CC charging model to hurt the financial bottom line of the users and the CSPs [10] by targeting the resource utilization at the application layer. EDoS attack is an economic security threat on the CC [10], which differs from a typical DDoS attack. DDoS attacks aim for service availability by debilitating the server's resources until the server crash or are unresponsive; however, EDoS exploits the resource flexibility provided by the CC to force over-consumption of resources [11,12]. The COVID-19 pandemic has affected everybody since 2020, from individuals to businesses, public services, and educational institutions. At the same time, the pandemic also drives the demand for online services, including CC. So, it is rational to assume that it would also increase DDoS attack incidents and could be even more prominent going forward. Several surveys investigated DDoS attacks on CC and their effects in the effort to find solutions to secure the CC. Unfortunately, the existing surveys fall short of covering all parameters and taxonomies in this field. Therefore, this paper attempts to fill in the missing gaps. This survey has the following contributions: (i) a qualitative comparison between this survey and the existing surveys in similar areas; (ii) a proposal of an author-defined taxonomy of attacks, DDoS attacks, and DDoS detection approaches on the CC environment; (iii) a comprehensive review of different types of DDoS attacks on CC and the techniques to detect them; and (iv) detailed explanations on the security issues and challenges of CC on the security, technological, and technical aspects. The rest of the paper is organized as follows: the explanation of CC and DDoS attacks is in Section 2. Section 3 discusses security issues and challenges in CC. Section 4 provides a qualitative comparison between this work and existing surveys. Section 5 provides the proposed taxonomy of the attacks, DDoS attacks, and DDoS attack detection approaches on CC. Section 6 touches on influential factors for choosing a DDoS attack detection strategy on CC.