The Cloud Security Alliance has taken a second run at creating recommendations for businesses to follow in order to better secure cloud services.

The new document aligns CSA's definition of cloud computing with that of the National Institute of Standards and Technology's (NIST) definition, which includes on-demand self service, broadband network access, resource pooling, rapid provisioning, scalability and metered usage.

NIST also divides cloud services into three categories: software-as-a-service (SaaS) (applications supplied by the service provider), platform-as-a-service (tools and programming languages supported by the provider for customers to deploy their own applications) and infrastructure-as-a-service (provider supplies hardware platforms within its network for customer use).

"Security Guidance for Critical Areas of Focus in Cloud Computing V2.1" compresses some of the topics that were considered in the earlier draft, and comes up with more specific recommendations in each of the 13 areas the 76-page document contains.

The document recommends cloud providers adopt the ISO/IEC 27001 standard for information security management systems. Customers should find out if their providers are certified and if not what their plans are for getting certified. At the least, providers should show that their practices are aligned with those set down by ISO 27002.

Customers need to realise that the type of cloud service they buy has an impact on how much responsibility they have for directly providing security and management of their data and applications, the report says. "The key takeaway for security architecture is that the lower down the stack the cloud service provider stops, the more security capabilities and management consumers are responsible for implementing and managing themselves," the report says.

For instance, Amazon's EC2 infrastructure as a service addresses physical, environmental and virtualisation security but not security of virtual instances, operating systems, applications and the data itself. With SaaS such as Salesforce.com's CRM offering, the provider is responsible for securing everything including the application and data.

Businesses must fully understand providers' security measures or run the risk of endangering their data. "Unless cloud providers can readily disclose their security controls and the extent to which they are implemented to the consumer, and the consumer knows which controls are needed to maintain the security of their information, there is tremendous potential for misguided decisions and detrimental outcomes," the report says.

In general, potential users of cloud services need to do a risk assessment that takes into account the importance of data to a business and the security that providers can provably deliver, the report says. "As with any security area, organisations should adopt a risk-based approach to moving to the cloud and selecting security options," the report says.

To do that the report recommends the following steps:

  • Determine exactly what data or function is being considered for the cloud.
  • Assess how important the data or function is to the organisation.
  • Determine which of the following cloud options are acceptable: public; private (internal); private (external); community; hybrid.
  • Evaluate the degree of control available to implement risk mitigations.
  • Map out the flow of data in and out of the cloud to identify points of exposure to risk.