In the AWS shared responsibility model, what does the phrase “security of the cloud” mean?

Security of the cloud" refers to AWS's responsibility for protecting the infrastructure that runs all of the services offered in the AWS Cloud. This includes the physical facilities, network infrastructure, hardware, and software that power AWS services. AWS is responsible for the operational aspects of security for this infrastructure. The availability of AWS services (like Amazon EC2) is a result of this security, but not the definition itself. Customer implementation of password policies for IAM users and security of customer environments using AWS Network Firewall partners fall under "security in the cloud," which is the customer's responsibility.