What is AWS Control Tower?

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AWS Control Tower

A multi-account strategy in AWS can provide you with a secure and isolated platform from which to launch your resources. Whilst smaller organizations may only require a few AWS accounts, large corporations with many business units often require many accounts. These accounts may be organized hierarchically.

Building this account topology manually on the cloud requires a high degree of knowledge, and is rather error prone. If you want to set up a multi-account environment in AWS within a few clicks, you can use a service called AWS Control Tower.

AWS Control Tower allows your team to quickly provision and to set up and govern a secure, multi-account AWS environment, known as a landing zone. Built on the back of AWS Organizations, it automatically implements many accounts under the appropriate organizational units, with hardened service control policies attached. Provisioning new accounts happens in the click of a button, automating security configuration, and ensuring you extend governance into new accounts, without any manual intervention.

There are a number of key features which constitute AWS Control Tower, and in this article, we will explore each section and break down how it makes governing multiple accounts a lot easier.

The Landing Zone

A Landing Zone refers to the multi-account structure itself, which is configured to provide with a compliant and secure set of accounts upon which to start building. A Landing Zone can include extended features like federated account access via SSO and the utilization of centralized logging via Amazon CloudTrail and AWS Config.

The Landing Zone’s accounts follow guardrails set by you to ensure you are compliant to your own security requirements. Guardrails are rules written in plain English, leveraging AWS CloudFormation in the background to establish a hardened account baseline.

Guardrails can fit into one of a number of categories:

Mandatory – These come pre-configured on the accounts and can not be removed. An example may be “Enable AWS Config in All Available Regions or Disallow Deletion of Log Archive.

Optional – These are useful but not always necessary depending on your use case, and are up to your discretion if you choose to use them. Some examples may be Detect Whether Public Read Access to Amazon S3 Buckets is Allowed and Detect Whether Amazon EBS Volumes are Attached to Amazon EC2 Instances.

Elective Guardrails – Elective guardrails allow you to lock down certain behaviors which are commonly restricted in an AWS environment. These guardrails are not enabled by default, and can be disabled at any time. Examples of these guardrails are the following: Detect Whether MFA is Enabled for AWS IAM Users and Detect Whether Versioning for Amazon S3 Buckets is Enabled.

Guardrails provide immediate protection from any number of scenarios, without the need to be able to read or write complex security policies – a big upside compared to manual provisioning of permissions.

Account Factory

Account Factory is a component of Control Tower which allows you to automate the secure provisioning of new accounts, which exist according to defined security principles. Several pre-approved configurations are included as part of the launch of your new accounts including Networking information, and Region Selection. You also get seamless integration with AWS Service Catalog to allow your internal customers to configure and build new accounts. Third party Infrastructure as Code tooling like Terraform (Account Factory for Terraform) can be used also to provide your cloud teams the ability to benefit from a multiple account setup whilst using tools they are familiar with.

Architecture of Control Tower

Lets now dive into how Control Tower looks, with an architectural overview.

As you can see, there are a number of OUs (Organizational Units) in which accounts are placed. These are provisioned for you using AWS Organizations.

  1. Security OU – The Security OU contains two accounts, the Log Archive Account and the Audit Account. The Log Archive Account serves as a central store for all CloudTrail and AWS Config logs across the Landing Zone, securely stored within an S3 Bucket.
  2. Sandbox OU – The Sandbox OU is setup to host testing accounts (Sandbox Accounts) which are safely isolated from any production workloads.
  3. Production OU – This OU is for hosting all of your production accounts, containing production workloads.
  4. Non-Production OU – This OU can serve as a pre-production environment, in which further testing and development can take place.
  5. Suspended OU – this is secure OU, where you can move any deleted, reused or breached accounts. Permissions in this OU are extremely locked-down, ensuring it is a safe location.
  6. Shared Services OU – The Shared Services OU contains accounts in which services shared across multiple other accounts are hosted. This consists of three accounts:
  • The Shared Services account (where the resources are directly shared)
  • The Security Services Account (hosting services like Amazon Inspector, Amazon Macie, AWS Secrets Manager as well as any firewall solutions.)
  • The Networking Account – This contains VPC Endpoints and components and things like DNS Endpoints.

Any organization can benefit from using AWS Control Tower. Whether you’re a multinational corporation with years of AWS Experience, or a burgeoning start-up with little experience in the cloud, Landing Zone can provide your customers with confidence that they are provisioning their architecture efficiently and securely.

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