"The firewall appliance sends logs to Amazon CloudWatch Logs and includes event severities of CRITICAL, HIGH, MEDIUM, LOW, and INFO"

* Step 1: Deploy the Automation Solution using CloudFormation StackSets To automate the process across multiple AWS accounts within an organization, you can use AWS CloudFormation StackSets. StackSets allow you to deploy CloudFormation templates to multiple accounts within an organization, ensuring consistent infrastructure and automation.
Action: Use AWS CloudFormation StackSets to deploy the necessary resources across all AWS accounts. This includes deploying the Lambda function and security groups that will isolate compromised EC2 instances.
Why: StackSets make it easy to deploy and manage resources across multiple AWS accounts, reducing the operational overhead.
Reference:
This corresponds to Option A: Use AWS CloudFormation StackSets to deploy the CloudFormation stacks in all AWS accounts.
* Step 2: Isolate EC2 Instances using Lambda and Security Groups
When an EC2 instance is compromised, it needs to be isolated from the network. This can be done by creating a security group with no inbound or outbound rules and attaching it to the instance. A Lambda function can handle this process and can be triggered automatically by an Amazon EventBridge rule when a specific tag (e.g., "isolation") is applied to the compromised instance.
Action: Create a Lambda function that attaches an isolated security group (with no inbound or outbound rules) to the compromised EC2 instances. Set up an EventBridge rule to trigger the Lambda function when the "isolation" tag is applied to the instance.
Why: This automates the isolation process, ensuring that any compromised instances are immediately cut off from the network, reducing the potential damage from the compromise.
This corresponds to Option E: Create an AWS CloudFormation template that creates an EC2 instance role that has no IAM policies attached. Configure the template to have a security group that has no inbound rules or outbound rules. Use the CloudFormation template to create an AWS Lambda function that attaches the IAM role to instances. Configure the Lambda function to replace any existing security groups with the new security group. Set up an Amazon EventBridge rule to invoke the Lambda function when a specific tag is applied to a compromised EC2 instance.

By default, the AWSCodeCommitPowerUser managed policy allows users to push changes to any branch in any repository in the AWS account. To restrict the developers' ability to push changes to the main branch directly, an additional policy is needed that explicitly denies these actions for the main branch.
The Deny rule should be included in a policy statement that targets the specific repositories and includes a condition that references the main branch. The policy statement should look something like this:
{
"Effect": "Deny",
"Action": [
"codecommit:GitPush",
"codecommit:PutFile"
],
"Resource": "arn:aws:codecommit:<region>:<account-id>:<repository-name>",
"Condition": {
"StringEqualsIfExists": {
"codecommit:References": [
"refs/heads/main"
]
}
}

https://aws.amazon.com/blogs/mt/how-to-centrally-manage-aws-iot-greengrass-devices-using-aws-systems-manager/?force_isolation=true