AWS Control Tower
A service that automates the setup and governance of multi-account AWS environments, centrally managing security and compliance baselines
Overview
AWS Control Tower is a service for securely and efficiently setting up and managing multi-account AWS environments. It automatically builds a Landing Zone based on best practices for multi-account architecture and enforces organization-wide security policies through guardrails (preventive and detective controls). Account Factory creates new accounts from templates in minutes, with guardrails automatically applied upon creation. It integrates Organizations, IAM Identity Center, CloudTrail, Config, and other AWS services in a unified configuration.
Guardrail Types and Application Strategy
Control Tower guardrails are classified into three types. Preventive guardrails are implemented via SCPs (Service Control Policies) and block prohibited operations - for example, preventing CloudTrail from being disabled or restricting resource creation to specific regions. These SCPs enforce restrictions across entire AWS accounts, providing a hard boundary that cannot be bypassed by any IAM principal within the account. Detective guardrails are implemented via Config rules and detect policy violations with notifications, allowing you to identify and remediate non-compliant resources. Proactive guardrails are implemented via CloudFormation hooks and validate templates before deployment to prevent non-compliant resources from being created in the first place. In practice, the recommended approach is to apply mandatory guardrails (enabled by default) along with strongly recommended guardrails for industry compliance requirements (PCI DSS, HIPAA, etc.) at the OU (Organizational Unit) level. Start with a conservative set and expand gradually as your organization's cloud maturity grows.
OU Structure and Account Factory Design
The most critical aspect of deploying Control Tower is OU structure design. The recommended configuration is a three-tier structure: Security OU (log archive and audit accounts), Infrastructure OU (shared networking and DNS), and Workloads OU (production and development environments). This separation ensures that security-critical resources are isolated from workload accounts and managed by a dedicated team. Using Account Factory Customization (AFC), you can automatically apply VPC settings, IAM roles, and security tool enablement when creating new accounts, fully automating account bootstrapping. Account Factory creates new accounts from templates in minutes with guardrails automatically applied upon creation, eliminating manual setup and ensuring consistent baselines. Unlike Azure Landing Zone, which is delivered as Bicep/Terraform templates that you deploy and customize yourself, Control Tower is a managed service that builds a landing zone with just a few clicks in the console. AWS account management books (Amazon) are a great resource for deeper understanding.
Introducing Control Tower to Existing Organizations Environments
When introducing Control Tower into an existing AWS Organizations environment, careful planning is required to avoid disruptions. The enrollment process brings existing accounts under Control Tower's governance, but you must verify potential conflicts with existing SCPs and Config rules beforehand. If existing SCPs are more restrictive than Control Tower's guardrails, the more restrictive policy takes effect, which is generally safe. However, if existing SCPs permit actions that Control Tower's guardrails block, enrolling accounts may break existing workflows that depend on those permissions. Before enrollment, audit each account's active Config rules to identify overlaps or conflicts with Control Tower's detective guardrails - duplicate rules waste evaluation costs and can produce confusing compliance reports. A phased rollout is recommended: start by enrolling a non-production account, verify that all existing workloads function correctly under the new guardrails, and then proceed to enroll production accounts. Document any exceptions or customizations needed for specific accounts before beginning the migration.