  In recent years, Cloud Computing has transformed local businesses and created
new business models on the Internet- and Cloud services are still flourishing.
But after the emphatic hype in the early years, a more realistic perception of
Cloud services has emerged. One reason for this surely is that today, Cloud
Computing is considered as an established and well-accepted technology and no
longer as a technical novelty. But the second reason for this assessment might
also be numerous security issues that Cloud Computing in general or specific
Cloud services have experienced since then. In this paper, we revisit attacks
on Cloud services and Cloud-related attack vectors that have been published in
recent years. We then consider successful or proposed solutions to cope with
these challenges. Based on these findings, we apply a security metric in order
to rank all these Cloud-related security challenges concerning their severity.
This should assist security professionals to prioritize their efforts toward
addressing these issues.
