Detections
Analytics

4.1 Ensure unauthorized API calls are monitored

Warning! Audit Deprecated

This audit has been deprecated and will be removed in a future update.

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Information

Real-time monitoring of API calls can be achieved by directing CloudTrail Logs to CloudWatch Logs or an external Security Information and Event Management (SIEM) environment, and establishing corresponding metric filters and alarms.

It is recommended that a metric filter and alarm be established for unauthorized API calls.

CloudWatch is an AWS native service that allows you to observe and monitor resources and applications. CloudTrail logs can also be sent to an external Security Information and Event Management (SIEM) environment for monitoring and alerting.

Monitoring unauthorized API calls will help reduce the time it takes to detect malicious activity and can alert you to potential security incidents.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

If you are using CloudTrail trails and CloudWatch, perform the following steps to set up the metric filter, alarm, SNS topic, and subscription:

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Create a metric filter based on the provided filter pattern that checks for unauthorized API calls and uses the <trail-log-group-name> taken from audit step 1:

aws logs put-metric-filter --log-group-name <trail-log-group-name> --filter-name <unauthorized-api-calls-metric> --metric-transformations metricName=unauthorized_api_calls_metric,metricNamespace=CISBenchmark,metricValue=1 --filter-pattern "{ ($.errorCode ="*UnauthorizedOperation") || ($.errorCode ="AccessDenied*") && ($.sourceIPAddress!="delivery.logs.amazonaws.com") && ($.eventName!="HeadBucket") }"

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

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Create an SNS topic that the alarm will notify:

aws sns create-topic --name <sns-topic-name>

Note : You can execute this command once and then reuse the same topic for all monitoring alarms.

Note : Capture the TopicArn that is displayed when creating the SNS topic in step 2.

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Create an SNS subscription for the topic created in step 2:

aws sns subscribe --topic-arn <sns-topic-arn> --protocol <sns-protocol> --notification-endpoint <sns-subscription-endpoints>

Note : You can execute this command once and then reuse the same subscription for all monitoring alarms.

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Create an alarm that is associated with the CloudWatch Logs metric filter created in step 1 and the SNS topic created in step 2:

aws cloudwatch put-metric-alarm --alarm-name "unauthorized_api_calls_alarm" --metric-name "unauthorized_api_calls_metric" --statistic Sum --period 300 --threshold 1 --comparison-operator GreaterThanOrEqualToThreshold --evaluation-periods 1 --namespace "CISBenchmark" --alarm-actions <sns-topic-arn>

Impact:

This alert may be triggered by normal read-only console activities that attempt to opportunistically gather optional information but gracefully fail if they lack the necessary permissions.

If an excessive number of alerts are generated, then an organization may wish to consider adding read access to the limited IAM user permissions solely to reduce the number of alerts.

In some cases, doing this may allow users to actually view some areas of the system; any additional access granted should be reviewed for alignment with the original limited IAM user intent.

See Also

https://workbench.cisecurity.org/benchmarks/19631

Item Details

References: CSCv7|6.3, CSCv7|6.5, CSCv7|6.7

Plugin: amazon_aws

Control ID: e1f162051b9262dd35a80abc50247f4e576fcde567080a6608f7d495c69c4132