Enable the require_ssl parameter for your Amazon Redshift cluster.
Rationale
Redshift clusters that do not require an SSL connection are vulnerable to exploits, such as man-in-the-middle attacks. Securing your connections protects your sensitive and private data.
Remediation
From the console
Amazon Redshift Clusters use AWS Certificate Manager (ACM)] to manage SSL certificates. To configure Redshift parameter groups in the console, follow the Managing parameter groups using the console docs.
From the command line
Run modify-cluster-parameter-group with name of the default parameter group you want to modify and the required parameters for SSL. This returns the group name and status if successful.