# Cyber-Storms Cone from Clouds: Security of Cloud Computing in the IoT Era
## 5 Cloud-Specific Security Issues
### Virtual Machine Introspection Issues  
Different literature works, such as [50; 56; 57], propose to use the hypervisor for monitoring virtual machines with the objective of preventing or discovering attacks on the integrity of guest systems. From the one hand, this kind of approach presents important advantages, on the other hand, it also highlights the possibility for the Cloud provider or malicious insiders (or even for an external attacker able to take control of the hosting platform) to break users' confidentiality by exploiting virtual machine introspection. This problem is linked to the more general and emblematic question of deciding whether the Cloud provider and the infrastructure it provides, should be considered trusted or not, a typical problem of every scenario in which outsourcing is present. It is worth noting that, in case the Cloud provider is considered trusted, the Cloud infrastructure might also play a key role in solving many of the existing security issues [58].  
An example of attack that can allow a malicious insider to exploit virtual machine introspection is described in [59].  
For the sake of completeness, it should also be mentioned that attacks targeting virtual machine introspection mechanisms have been reported in the literature. An example of such an attack is Direct Kernel Structure Manipulation (DKSM) [60].  
VM Management Issues  
VM image cloning enables Cloud providers to supply on-demand services to their clients. Cloned VMs can be moved on different servers in relation to clients' needs but this also makes clients unaware of how many VMs copies exist, where these are specifically located and who is possessing them. Such availability, allows a malicious insider to exploit one of the existing VM copies to attempt breaking the VM password and gain access to all the information saved into the VM [61] while leaving the owner unaware of such situation.  
VM image sharing is another key service enabled by VM image cloning. VM image sharing is one of the Cloud foundations [62], however, both the VM image publisher and the retriever are subject to confidentiality concerns [63]. Indeed, by publishing an image, the publisher may release his own confidential information, while, on the other side, user's data confidentiality can be compromised by shared malicious images, for instance, they can contain backdoors for silently access confidential data [64; 26]. Moreover, VM image sharing makes also possible for attackers to rent cloned VMs with the only purpose of analyzing their content and therefore to identify possible vulnerabilities that could be exploited in future attacks. Consequently, from the confidentiality point of view this can have a dangerous effect not only on Cloud providers that manage such VMs, but on the IoT end devices as well.  
VM Migration Issues  
Virtual Machine migration allows to transfer running VMs from one host to another in a transparent fashion for the final user [65; 66]. The Cloud advantages of using such mechanisms are obvious, just to name a few: enables load-balance when hosts are overloaded, allows to reduce costs through VMs consolidation, and improves the overall manageability of the system [65; 66; 67]. However, protocols used in implementing live migration have to be secured: if control messages and migrating VMs are not encrypted, common attacks on confidentiality (such as passwords eavesdropping) might be easily performed [65; 68].