# Cyber-Storms Cone from Clouds: Security of Cloud Computing in the IoT Era
## 4 Methodology
### Structured Classification  
In this section, we describe how our reference architecture is adopted to classify Cloud security issues. The overall classification is depicted in Figure 5.  
Figure 4: Simplified Cloud reference architecture. Figure 5: Classification of Cloud security issues. Firstly, we separate Cloud-specific security issues from generic ones. Details about the criteria used for performing such distinction are provided in Section 5. In short, many security issues of the Cloud exist also in other paradigms, since rooted in common technologies employed to build distributed systems. Thus, we distinguish between issues that we consider specific of the Cloud environment and other common security issues not strictly related to the Cloud but still having an impact on the overall IoT architecture (depicted in Figure 1). However, even if we also present a subset of generic security issues, our main focus is on Cloud-specific ones. Secondly, security issues are further classified from two different perspectives: the Cloud architectural level at which they occur and the security property they affect. In other words, given a certain level \(x\) of the Cloud reference architecture and a certain security property \(y\), the following questions are answered: _(1) What are the security problems at level \(x\) of the Cloud architecture?_, _(2) How do they affect property \(y\)?_ In answering these questions, the security properties we consider are the well-known confidentiality, integrity, and availability (CIA). We have decided to stick only with these security properties to keep the scope of the paper well focused and manageable in terms of literature and analysis. However, the same methodology can be applied to and iterated with other security properties (e.g., authenticity and accountability). The classification resulting from the analysis described in Sections 5 and 6 is depicted at the end of the paper in Tables 1 and 2, respectively. These tables show each issue in relation to the architectural level it occurs and the CIA property it affects. For each cell of the table (associated with a specific pair: issue, security property) a mark is applied according to the following rules:  
* \"\(\check{\check{\check{\check{\check{\check{\check{\check{\check{\check{\check{\check{ \check{\check{\ \begin{table}
\begin{tabular}{l l c c c c} \hline \hline
**Architectural Level** & **Issues** & **Conidentiality** & **Integrity** & **Availability** & **Exploited/Victor (_Cloud, IoT Devices, Both_)** \\ \hline \multirow{4}{*}{Virtualization} & Multi-tenancy & ✓ & ✓ & ✓ & Cloud/ IoT devices \\  & VM isolation & ✓ & ✓ & ✓ & Cloud/ IoT devices \\  & Virtual network & ✓ & ✓ & ✓ & Both/ Both \\  & VM intoreception & ✓ & ✓ & & Cloud/ IoT devices \\  & VM management & ✓ & ✓ & ✓ & Cloud/Both \\  & VM migration & ✓ & ✓ & ✓ & Both/ IoT devices \\ \hline \multirow{4}{*}{Application} & Isolation & ✓ & ✓ & ✓ & Cloud/ IoT devices \\  & Synchronization mechanisms & ✓ & ✓ & ✓ & Both/ IoT devices \\  & Insecure APIs, management and control interfaces & \(\sim\) & ✓ & ✓ & Both/Both \\  & Resource accounting & & & ✓ & IoT devices/Cloud \\ \hline Network & Network under-provision & & & ✓ & Both/Both \\ \hline Data Storage & Outsourcing & ✓ & ✓ & & Cloud/ IoT devices \\  & Data deletion & ✓ & & & Cloud/ IoT devices \\ \hline Multi-level & Economic sustainability & & & ✓ & Both/IoT devices \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of Cloud-specific issues. “_/_”: existence of literature works indicating that the issue affects the property. “_/_”: despite we found no evidence in the literature, we believe that the issue might affect the property. Exploited/Victor: how parties of the IoT architecture (Figure 1) are affected from the issue.