Cis AWS Compute 2.12

Ensure EBS volumes attached to an EC2 instance are marked for deletion upon instance termination

Description

This rule ensures that Amazon Elastic Block Store volumes that are attached to Amazon Elastic Compute Cloud (Amazon EC2) instances are marked for deletion when an instance is terminated. If an Amazon EBS volume isn't deleted when the instance that it's attached to is terminated, it may violate the concept of least functionality.

Rationale

Orphaned EBS volumes after instance termination can contain sensitive data and increase costs. Marking volumes for deletion on termination ensures cleanup.

Impact

Data on the EBS volume will be permanently lost when the instance is terminated. Ensure important data is backed up before enabling this setting.

Audit Procedure

Using AWS CLI

1. Run the describe-instances command:

aws ec2 describe-instances --region us-east-1 --output json --filters "Name=block-device-mapping.delete-on-termination,Values=false" --query "Reservations[*].Instances[*].{Instance:InstanceId}"

2. The output should be a list of instances that have not set 'Delete on termination'.
3. Make note of the list of instance ids and refer to the remediation below.
4. Repeat steps no. 1 -3 with the other AWS regions.

Using AWS Console

1. Login to EC2 using https://console.aws.amazon.com/ec2/
2. On the left Click INSTANCES, click Instances.
3. Select the EC2 instance you want to review.
4. Select the Storage tab.
5. Scroll down until you reach the 'Volume ID' and review the setting for 'Delete on termination'.
6. If the value is set to No refer to the remediation below.
7. Repeat steps no. 3 - 6 to verify the setting.
8. Go through the other AWS regions and repeat the audit process for all instances.

Expected Result

The CLI command should return an empty list, indicating all EBS volumes attached to instances have DeleteOnTermination set to true.

Remediation

Using AWS CLI

1. Run the modify-instance-attribute command using the list of instances collected in the audit:

aws ec2 modify-instance-attribute --instance-id i-123456abcdefghi0 --block-device-mappings "[{\"DeviceName\": \"/dev/sda\",\"Ebs\":{\"DeleteOnTermination\":true}}]"

2. Repeat steps no. 1 with the other instances discovered in all AWS regions.

Note: If you get any errors running the modify-instance-attribute command confirm the instance id and the Device Name for that instance is correct. The above command is referencing the typical default device name.

Using AWS Console

1. At this time the delete on termination setting for existing instances can only be changed using AWS CLI.

Default Value

By default, the root EBS volume is marked for deletion on termination, but additional attached volumes are not.

References

1. https://awscli.amazonaws.com/v2/documentation/api/latest/reference/ec2/modify-instance-attribute.html
2. https://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeInstances.html

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Level 1 | Manual