# Secure Cloud Infrastructure: A Survey on Issues, Current Solutions, and Open Challenges
## 5 Related Existing Solutions in Cloud Levels
### Solutions at Host Level
In addition, the SCORE tool was defined in this paper [102] as an extension to the Google Omega lightweight simulator, which is devoted to the simulation of energy-efficient monolithic and parallel-scheduling models as well as the execution of heterogeneous, realistic, and synthetic workloads. Empirical tests were used to evaluate the simulator. The experiment results confirm that SCORE is a performant and reliable tool for testing energy efficiency, security, and scheduling strategies in cloud computing environments. At this level, the majority of solutions employed IDS/IPS models to detecting and preventing hypervisor attacks and identifying malicious activities inside the system. However, the cloud is a large-scale and heterogeneous environment that needs to mitigate the risks of hypervisors in multiple VMs, while some studies, such as [93], focused on mitigating risks on hypervisors in single VMs only. Furthermore, some solutions were customized to specific scenarios, known patterns of attacks, or even specific software [92; 94]. To conclude, the proposed solutions should consider some serious attacks such as the distributed side-channel attacks while designing their detection or prevention techniques. These attacks are major threats to cloud infrastructures that can be used to exploit sensitive data from various parts of a distributed system [95]. The host-level techniques are still not fully mature, in which these techniques need to immediately respond, automatically block malicious events, and take appropriate action to prevent attacks from happening. Table 4 presents a summary of the existing solutions in the literature according to the four levels discussed in the previous subsections. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Level Name** & **Techniques** & **Limitations** & **References** \\ \hline \multirow{4}{*}{Data Level} & Data loss or leakage used a technique to secure data are by applying encryption mechanisms like TLS, AES and SHA & The encryption techniques are still not fully mature and face many problems & [9; 37; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62] & The available technique to classification is consumes resources & [9; 37; 50; 62] \\  & Classification technique to have security levels for data & The existing techniques deal with simple DDoS attacks only, while the nature of the cloud needs techniques can prevent and detect the complex attacks and unknown patterns & [6; 38; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80] \\ \hline \multirow{4}{*}{Application Level} & IDS/IPS techniques were used to solve EDoS attacks & The techniques used to solve simple attacks & [6; 38; 64; 65; 66; 67; 68; 69; 70; 72; 73; 74; 76; 77; 78; 79; 80] \\  & The techniques to solve poor authentication are identity management system (IDMS), and also some authentication based on AES and MD5 & Testing environments and use a small amount of data are considered barriers against implementation.The traditional access control and identity management are not suitable to promote security & \\ \hline \multirow{4}{*}{Network Level} & Some of DDoS/DoS techniques did not deal with IP spoofing where these attacks often use IP spoofing to overload networks; therefore, it is unable to differentiate between good traffic and bad traffic & [7; 81; 82; 83; 84; 85; 86; 87; 88; 89] \\  & The techniques of DNS issues vary between dynamic firewalls and IDS & Some of DDoS/DoS techniques did not deal with IP spoofing where these attacks often use IP spoofing to overload networks; therefore, it is unable to differentiate between good traffic and bad traffic & [7; 81; 82; 83; 84; 85; 86; 87; 88; 89] \\ \cline{1-1}  & & These techniques did not take into consideration some of the serious attacks such as Man in the middle attack, modified data attack, DNS ID spoofing attack, corrupted data attack,... etc. & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of existing solutions in the literature.