Why is cloud security considered hard?

One of the main reasons why cloud security is considered challenging is potentially due to the lack of full control of the environment. Along with the lack of control, lack of visibility is also one of the challenges as we don't really know how things look behind the scenes.

Since cloud environment is a giant resource pool, we generally share the underlying resources with multiple other users belonging to different organizations. This is often referred as multi-tenancy.

Since the resource is generally not dedicated to us, we are not allowed to do various things, such as performing external scans on our websites, that might affect the performance of other customers. There are many such reasons that causes a bit of limitations in terms of flexibility and visibility in cloud environments.