## 2 Security Benefits and Challenges in Cloud Computing  
Cloud Computing is not necessarily more or less secure than the current environment although it does create new risks, new threats, new challenges and new opportunities as with any new technology. In some cases moving to the cloud provides an opportunity to re-architect older applications and infrastructure to meet or exceed modern security requirements. At other times the risk of moving sensitive data and applications to an emerging infrastructure might exceed the required tolerance [3]. Although there is a significant benefit to leveraging Cloud computing, security concerns have led organizations to hesitate to move critical resources to the cloud. Corporations and individuals are often concerned about how security and compliance integrity can be maintained in this new environment [7]. With the cloud model, you lose control over physical security due to the fact that you are sharing computing resources with other companies (for public cloud) and moreover, if you should decide to move the storage services provided by one cloud vendor's services to another one, these storage services may be incompatible with another vendor's services. It is recommended that your development tool of choice should have a security model embedded in it to guide developers during the development phase and restrict users only to their authorized data when the system is deployed into production [7, 18]. In the rush to take advantage of the benefits of Cloud computing, not least of which is significant cost savings, many corporations are seemingly rushing into Cloud computing without a serious consideration of the security implications. To overcome the customer concerns about application and data security, vendors must address these issues head-on. There is a strong apprehension about insider breaches, along with vulnerabilities in the applications and systems' availability that could lead to loss of sensitive data and money. Such challenges can dissuade enterprises from adopting applications within the cloud [18]. Therefore, the focus is not upon portability of applications, but on preserving or enhancing the security functionality provided by the legacy application and achieving a successful application migration [3]. The cloud providers and vendors have advanced in this direction improving the security aspects and solutions which are offered to the customers who wish to move their applications and data to cloud, and becoming a very attractive paradigm because of perceived economic and operational benefits. Among this attractive set of benefits one can find the security benefits which are offered by the cloud providers to their customers who choose to move their applications to the cloud [11, 19, 20]. Among the most popular security benefits in Cloud computing we can define the following:  
* Security and benefits of scale: put simply, all kinds of security measures are cheaper when implemented on a larger scale due to the massive concentration of resources however the data presents a more attractive target to attackers, but cloud-based defenses can be more robust, scalable and cost-effective. This includes all kinds of defensive measures such as filtering, patch management, hardening of virtual machine instances and hypervisors, _etc_. * Security as a market differentiator: security is a priority concern for many cloud customers; many of whom will make buying choices on the basis of the reputation for confidentiality, integrity and resilience of the provider as well as the security services offered by the provider. * Standardized interfaces for managed security services: large cloud providers can offer a standardized, open interface to managed security services providers. This creates a more open and readily available market for security services.