Profile Applicability: Level 1


Description: 

Real-time monitoring of API calls can be achieved by directing CloudTrail Logs to CloudWatch Logs and establishing corresponding metric filters and alarms. It is recommended that a metric filter and alarm be established for changes to S3 bucket policies. 


Rationale: 

Monitoring changes to S3 bucket policies may reduce time to detect and correct permissive policies on sensitive S3 buckets. 


Audit: 

Perform the following to ensure that there is at least one active multi-region CloudTrail with prescribed metric filters and alarms configured: 

1. Identify the log group name configured for use with active multi-region CloudTrail: 

List all CloudTrails: aws cloudtrail describe-trails 

Identify Multi region Cloudtrails: Trails with "IsMultiRegionTrail" set to true 

From value associated with CloudWatchLogsLogGroupArn

2. Get a list of all associated metric filters for this : aws logs describe-metric-filters --log-group-name "" 

3. Ensure the output from the above command contains the following: "filterPattern": "{ $.userIdentity.type = "Root" && $.userIdentity.invokedBy NOT EXISTS && $.eventType != "AwsServiceEvent" }" 

4. Note the  value associated with the filterPattern found in step 3. 

5. Get a list of CloudWatch alarms and filter on the  captured in step 4. aws cloudwatch describe-alarms --query 'MetricAlarms[?MetricName== ``]' 

6. Note the AlarmActions value - this will provide the SNS topic ARN value. 

7. Ensure there is at least one active subscriber to the SNS topic aws sns list-subscriptions-by-topic --topic-arn at least one subscription should have "SubscriptionArn" with valid aws ARN. Example of valid "SubscriptionArn": "arn:aws:sns::::"


Remediation:

Perform the following to setup the metric filter, alarm, SNS topic, and subscription: 

1. Create a metric filter based on filter pattern provided which checks for "Root" account usage and the  taken from audit step 1. aws logs put-metric-filter --log-group-name `` -- filter-name `` --metric-transformations metricName= `` ,metricNamespace='CISBenchmark',metricValue=1 --filterpattern '{ $.userIdentity.type = "Root" && $.userIdentity.invokedBy NOT EXISTS && $.eventType != "AwsServiceEvent" }'

Note: You can choose your own metricName and metricNamespace strings. Using the same metricNamespace for all Foundations Benchmark metrics will group them together. 

2. Create an SNS topic that the alarm will notify aws sns create-topic --name Note: you can execute this command once and then re-use the same topic for all monitoring alarms. 

3. Create an SNS subscription to the topic created in step 2 aws sns subscribe --topic-arn  --protocol  - -notification-endpoint Note: you can execute this command once and then re-use the SNS subscription for all monitoring alarms. 

4. Create an alarm that is associated with the CloudWatch Logs Metric Filter created in step 1 and an SNS topic created in step 2 aws cloudwatch put-metric-alarm --alarm-name `` --metricname `` --statistic Sum --period 300 --threshold 1 -- comparison-operator GreaterThanOrEqualToThreshold --evaluation-periods 1 -- namespace 'CISBenchmark' --alarm-actions


Impact: 

Note: By default, CloudWatch Logs will store Logs indefinitely unless a specific retention period is defined for the log group. When choosing the number of days to retain, keep in mind the average days it takes an organization to realize they have been breached is 210 days (at the time of this writing). Since additional time is required to research a breach, a minimum 365 day retention policy allows time for detection and research. You may also wish to archive the logs to a cheaper storage service rather than simply deleting them. See the following AWS resource to manage CloudWatch Logs retention periods: 

    1. http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/SettingLogRetention.html 


References: 

1. CCE-79193-9 

2. https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudwatch-alarmsfor-cloudtrail.html 

3. https://docs.aws.amazon.com/awscloudtrail/latest/userguide/receive-cloudtraillog-files-from-multiple-regions.html 

4. https://docs.aws.amazon.com/sns/latest/dg/SubscribeTopic.html

Notes: Configuring log metric filter and alarm on Multi-region (global) CloudTrail 

  • Ensures that activities from all regions (used as well as unused) are monitored 
  • Ensures that activities on all supported global services are monitored 
  • Ensures that all management events across all regions are monitored


CIS Controls:

6.2 Activate audit logging 

    Ensure that local logging has been enabled on all systems and networking devices. 

14 Controlled Access Based on the Need to Know 

    Controlled Access Based on the Need to Know