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Enable CloudWatch Alarm for AWS EC2 Instance Changes

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Risk level: Medium (should be achieved)

Ensure there is an Amazon CloudWatch alarm available in your AWS account that is triggered each time an AWS EC2 instance configuration and status change is made. This CloudWatch alarm must fire every time an AWS API call is performed to create, terminate, start, stop or reboot an EC2 instance.

This rule resolution is part of the Cloud Conformity Base Auditing Package

Using Amazon CloudWatch alarms to detect EC2 instance configuration and status changes will help you stay up-to-date on the resource availability, gain insights into auto-scaling lifecycle, mitigate downtime, prevent data loss or avoid unexpected charges on your AWS bill. Note 1: For this rule Cloud Conformity assumes that the CloudTrail service is already enabled to stream event log data to CloudWatch within your AWS account, otherwise see this rule to enable AWS Cloudtrail – CloudWatch integration.
Note 2: You have also the option to implement this conformity rule with AWS CloudFormation. Download the required CloudFormation template from this URL and follow the AWS instructions available here.

Audit

Using AWS Console

01 Sign in to the AWS Management Console.

02 Navigate to Cloudwatch dashboard at https://console.aws.amazon.com/cloudwatch/.

03 In the left navigation panel select Alarms.

04 Open the dashboard Show/Hide Columns dialog box by clicking the configuration icon:

Open the dashboard Show/Hide Columns dialog box by clicking the configuration icon

then select the Metric Name checkbox.

05 In the Metric Name column, verify each alarm available for the EC2InstanceEventCount metric parameter name. If the EC2InstanceEventCount metric is not used by any of your existing alarms, the configuration/status changes made to your AWS EC2 instances are not monitored using Amazon CloudWatch.

06 Change the AWS region from the navigation bar and repeat the audit process for other regions.

Using AWS CLI

01 Run describe-alarms-for-metric command (OSX/Linux/UNIX) to list all AWS CloudWatch alarms that are currently associated with the EC2InstanceEventCount metric, available in the selected region:

aws cloudwatch describe-alarms-for-metric
    --region us-east-1
    --metric-name EC2InstanceEventCount
    --namespace AWS/CloudTrailMetrics

01The command output should return an array with the requested CloudWatch alarm(s) metadata:

{
    "MetricAlarms": []
}

If the command output returns an empty array as the value for the MetricAlarms property (as shown in the example above), there are no CloudWatch alarms currently set to monitor EC2 instances configuration/status changes such as create, start, stop, reboot or terminate.

01 Perform step no. 1 and 2 to repeat the audit process for other AWS regions.

Remediation / Resolution

Step 1: Create a Simple Notification Service (SNS) topic and the necessary subscription to send email notifications whenever the appropriate Amazon CloudWatch alarm is triggered.

Using AWS Console

01 Sign in to the AWS Management Console.

02 Navigate to SNS dashboard at https://console.aws.amazon.com/sns/v2/.

03 In the navigation panel, select Topics and click the Create new topic button.

04 In the Create new topic dialog box, enter a name and a display name for your topic then click Create Topic.

05 Open the newly created SNS topic configuration page by clicking on its Amazon Resource Name (ARN):

Open the newly created SNS topic configuration page by clicking on its Amazon Resource Name.

06 Under Subscription section click Create Subscription.

07 Select Email as subscription protocol from the Protocol dropdown list.

08 In the Endpoint box, enter the email address where you want to receive the CloudWatch alarm notifications then click Create Subscription to create the required subscription.

09 Use your preferred email client application to open the message received from AWS Notifications then click on the appropriate link to confirm your subscription.

Using AWS CLI

01 Run create-topic command (OSX/Linux/UNIX) to create a new SNS topic for sending email notifications whenever your AWS CloudWatch alarm is triggered:

aws sns create-topic
    --name CloudWatchAlarmSNSTopic

02 The command output should return the new SNS topic Amazon Resource Name (ARN):

{
  "TopicArn": "arn:aws:sns:us-east-1:123456789012:CloudWatchAlarmSNSTopic"
}

03 Run subscribe command (OSX/Linux/UNIX) to send the subscription confirmation message to the notification endpoint (i.e. the email address provided):

aws sns subscribe
    --topic-arn arn:aws:sns:us-east-1:123456789012:CloudWatchAlarmSNSTopic
    --protocol email
    --notification-endpoint no-reply@cloudconformity.com

04 Run confirm-subscription command (OSX/Linux/UNIX) to confirm the email subscription by validating the token sent to the notification endpoint selected (the command does not return an output):

aws sns confirm-subscription
    --topic-arn arn:aws:sns:us-east-1:123456789012:CloudWatchAlarmSNSTopic
    --token 66d8192f37fb687f5d51e6e241d7700ae02f7124d8268910b858cb4db727ceeb2474bb937929d3bdd7ce5d0cce19325d036bc858d3c217426bcafa9c501a2cace93b83f1dd3797627467553dc438a8c974119496fc3eff026eaa5d14472ded6f9a5c43aec62d83ef5f49109da71f1150

Step 2: Create the necessary metric filter and the CloudWatch alarm that will fire and send email notifications whenever an AWS EC2 instance configuration/status will change.

Using AWS Console

01 Sign in to the AWS Management Console.

02 Navigate to Cloudwatch dashboard at https://console.aws.amazon.com/cloudwatch/.

03 In the left navigation panel, select Logs.

04 Select the log group created for your CloudTrail trail event logs and click Create Metric Filter button.

05 On the Define Logs Metric Filter page, paste the following pattern inside the Filter Pattern box: { ($.eventName = RunInstances) || ($.eventName = RebootInstances) || ($.eventName = StartInstances) || ($.eventName = StopInstances) || ($.eventName = TerminateInstances) }. This pattern will be used for scanning the AWS CloudTrail logs for event names like “RunInstances”, “RebootInstances” or “TerminateInstances”.

06 Review the metric filter config details then click Assign Metric.

07 On the Create Metric Filter and Assign a Metric page, perform the following:

  1. In the Filter Name box, enter a unique name for the new filter, e.g. EC2InstanceStatusChanges.
  2. In the Metric Namespace box, type CloudTrailMetrics.
  3. In the Metric Name box, type EC2InstanceEventCount for the metric identifier.
  4. Click Show advanced metric settings to slide down the advanced settings section.
  5. In the Metric Value box, enter 1.

08 Review the details then click Create Filter to generate your new CloudWatch Logs metric filter.

09 On the current page click Create Alarm:

Create Alarm.

10 In the Create Alarm dialog box, provide the following information:

  1. Within the Alarm Threshold section, in the Name and Description fields, enter a unique name and a short description for the new CloudWatch alarm.
  2. Under Whenever: <Metric Name>, select >= (greater than or equal to) from the is dropdown list and enter 1 as the threshold value in the box next to the dropdown list to trigger the alarm every time a configuration or a status change involving an AWS EC2 instance is made.
  3. In the Actions section, click the + Notification button, select State is ALARM from the Whenever this alarm dropdown menu and choose the AWS SNS topic name created at Step 1 from Send notification to.
  4. In the Alarm Preview section, select 5 Minutes from the Period dropdown list and Sum from the Statistic list.
  5. Review the CloudWatch alarm configuration details then click Create Alarm. Once created, the new alarm will be listed on the Alarms page.

Using AWS CLI

01 Run put-metric-filter command (OSX/Linux/UNIX) to create the necessary CloudWatch metric filter and associate it with your appropriate Amazon CloudTrail log group (the command does not return an output):

aws logs put-metric-filter
    --region us-east-1
    --log-group-name CloudTrail/CloudWatchLogGroup
    --filter-name EC2InstanceStatusChanges
    --filter-pattern '{ ($.eventName = RunInstances) || ($.eventName = RebootInstances) || ($.eventName = StartInstances) || ($.eventName = StopInstances) || ($.eventName = TerminateInstances) }'
    --metric-transformations metricName=EC2InstanceEventCount,metricNamespace=CloudTrailMetrics,metricValue=1

02 Run put-metric-alarm command (OSX/Linux/UNIX) to create the AWS CloudWatch alarm that will fire whenever an AWS EC2 instance configuration/status change will be made (the command does not return an output):

aws cloudwatch put-metric-alarm
    --region us-east-1
    --alarm-name EC2InstanceChangesAlarm
    --alarm-description "Triggered by EC2 instances config/status changes."
    --metric-name EC2InstanceEventCount
    --namespace CloudTrailMetrics
    --statistic Sum
    --comparison-operator GreaterThanOrEqualToThreshold
    --evaluation-periods 1
    --period 300
    --threshold 1
    --actions-enabled
    --alarm-actions arn:aws:sns:us-east-1:123456789012:CloudWatchAlarmSNSTopic

References

Publication date Sep 16, 2016