Cloud comes in many flavours. There is SaaS (hosted applications like Dropbox, GSuite, Office365, Salesforce). There is PaaS (e.g. a managed database). There is IaaS (e.g. virtual machines and networks).
Cloud can be public (all instances are part of the public Internet, and run on shared infrastructure). It can be private (an elastic pool of capacity runs on hardware dedicated to you), and there is 'virtual private cloud' which emulates the latter on the former.
Traditional IT security architectures have emphasized 'perimeter security'. A set of VLAN's, controlled physical access, and firewalls at the door. The outside is evil, the inside is trusted. Suddenly a wild cloud appears and there is no longer an 'outside' or 'inside' or even 'door' to place the firewall. Is this your only concern?
In this webinar learn about some of the security 'surprises', and how you might embrace them rather than fear them.