A service control policy (SCP) is a type of policy that you can use to manage permissions in your organization. SCPs offer central control over the maximum available permissions for all accounts in your organization, allowing you to ensure your accounts stay within your organization’s access control guidelines. SCPs are available only in an organization that has all features enabled. SCPs do not grant permissions; instead, they specify the maximum permissions for an organization or organizational unit (OU). SCPs limit permissions that identity-basedpolicies or resource-based policies grant to entities (users or roles) within the account, but do not grant permissions to entities. You can use SCPs to restrict the actions that the root user in an account can perform. You can also use SCPs to prevent users or roles in any account from creating or modifying certain AWS resources, such as EC2 instances with public IP addresses or IAM resources with inline policies or “". For example, you can create an SCP that denies the ec2:RunInstances action if the request includes the AssociatePublicIpAddress parameter set to true. You can also create an SCP that denies the iam:PutUserPolicy and iam:PutRolePolicy actions if the request includes a policy document that contains "”. By attaching these SCPs to your organization or OUs, you can prevent the deployment of AWS CloudFormation stacks that violate these rules.
AWS Control Tower proactive controls are guardrails that enforce preventive policies on your accounts and resources. Proactive guardrails are implemented as AWS Organizations service control policies (SCPs) and AWS Config rules. However, AWS Control Tower does not provide a built-in proactive guardrail to block EC2 instances with public IP addresses or IAM resources with inline policies or “*”. You would have to create your own custom guardrails using AWS CloudFormation templates and SCPs, which is essentially the same as option D. Therefore, option A is not correct.
AWS Control Tower detective controls are guardrails that detect and alert on policy violations in your accounts and resources. Detective guardrails are implemented as AWS Config rules and Amazon CloudWatch alarms. Detective guardrails do not block or remediate noncompliant resources; they only notify you of the issues. Therefore, option B is not correct.
AWS Config is a service that enables you to assess, audit, and evaluate the configurations of your AWS resources. AWS Config continuously monitors and records your AWS resource configurations and allows you to automate the evaluation of recorded configurations against desired configurations. AWS Config rules are customizable, AWS Lambda functions that AWS Config invokes to evaluate your AWS resource configurations. You can use AWS Config rules to check for compliance with your policies, such as ensuring that EC2 instances have public IP addresses disabled or IAM resources do not have inline policies or “*”. However, AWS Config rules alone cannot prevent the deployment of AWS CloudFormation stacks that violate these policies; they can only report the compliance status. You would need to use another service, such as AWS Systems Manager Session Manager, to run automation scripts to delete or modify the noncompliant resources. This would require additional configuration and permissions, and may not be the most efficient or secure way to enforce your policies. Therefore, option C is not correct.
[References:, Service Control Policies, AWS Control Tower Guardrails, AWS Config, , , ]
