Containers are code execution environments that run within an operating system(for now), sharing and leveraging resources of that operating system. While a VM is a full abstraction of an operating system, a container is a constrained place to run segregated processes while still utilizing the kernel and other capabilities of the base 0S. Multiple containers can run on the same virtual machine or be implemented without the use of VMs at all and run directly on hardware.
Reference: CSA Security Guidelines V.4(reproduced here for the educational purpose)

There are three, commonly accepted forms of Controls:
Administrative-These are the laws, regulations, policies, practices and guidelines that govern the overall requirements and controls for an Information Security or other operational risk program. For example, a law or regulation may require merchants and financial institutions to protect and implement controls for customer account data to prevent identity theft. The business, in order to comply with the law or regulation, may adopt policies and procedures laying out the internal requirements for protecting this data, which requirements are a form of control.
Logical -These are the virtual, application and technical controls (systems and software), such as firewalls, antivirus software, encryption and maker/checker application routines.
Physical -Whereas a firewall provides a "logical" key to obtain access to a network, a "physical" key to a door can be used to gain access to an office space or storage room. Other examples of physical controls are video surveillance systems, gates and barricades, the use of guards or other personnel to govern access to an office, and remote backup facilities.

The characteristics of cloud computing are
1. 0n-demand self-service: A consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with each service provider.
2. Broad network access: Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms(e.g, mobile phones, tablets, laptops and workstations).
3. Resource pooling: The provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to consumer demand. There is a sense of location independence in that the customer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction(e.g, country, state or datacenter).
Examples of resources include storage, processing, memory and network bandwidth.
4. Rapid elasticity: Capabilities can be elastically provisioned and released, in some cases automatically, to scale rapidly outward and inward commensurate with demand. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be appropriated in any quantity at anytime.
5. Measured service: Cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service(e.g, storage, processing, bandwidth and active user accounts).
Resource usage can be monitored, controlled and reported, providing transparency for the provider and consumer.

Encryption of Data would have minimised the impact of the incident and it would have prevented data being used for scam calls.

Environmental Risk are not defined as a category in the ENISA document however. all the other three are defined as categories.