Detections
Analytics

4.12 Ensure changes to network gateways are monitored

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.

Network gateways are required to send and receive traffic to a destination outside of a VPC. It is recommended that a metric filter and alarm be established for changes to network gateways.

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 changes to network gateways will help ensure that all ingress/egress traffic traverses the VPC border via a controlled path.

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 network gateways changes 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 <network-gw-changes-metric> --metric-transformations metricName=<network-gw-changes-metric>,metricNamespace='CISBenchmark',metricValue=1 --filter-pattern '{ ($.eventName = CreateCustomerGateway) || ($.eventName = DeleteCustomerGateway) || ($.eventName = AttachInternetGateway) || ($.eventName = CreateInternetGateway) || ($.eventName = DeleteInternetGateway) || ($.eventName = DetachInternetGateway) }'

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 <network-gw-changes-alarm> --metric-name <network-gw-changes-metric> --statistic Sum --period 300 --threshold 1 --comparison-operator GreaterThanOrEqualToThreshold --evaluation-periods 1 --namespace 'CISBenchmark' --alarm-actions <sns-topic-arn>
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Implement logging and alerting mechanisms:

aws sns create-topic --name NetworkGatewayChangesAlerts

`

```aws sns subscribe --topic-arn <sns-topic-arn> --protocol email --notification-endpoint <email-address>``````aws cloudwatch put-metric-alarm --alarm-name NetworkGatewayChangesAlarm --metric-name GatewayChanges --namespace AWS/EC2 --statistic Sum --period 300 --threshold 1 --comparison-operator GreaterThanOrEqualToThreshold --evaluation-periods 1 --alarm-actions <sns-topic-arn>```

Impact:

Monitoring changes to network gateways helps detect unauthorized modifications that could compromise network security. Implementing automated monitoring and alerts can improve incident response times, but it may require additional configuration and maintenance efforts.

See Also

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

Item Details

Category: AUDIT AND ACCOUNTABILITY

References: 800-53|AU-3, 800-53|AU-3(1), 800-53|AU-6, 800-53|AU-6(1), 800-53|AU-7, 800-53|AU-7(1), 800-53|AU-12, CSCv7|6.2, CSCv7|6.3, CSCv7|11.3

Plugin: amazon_aws

Control ID: e2be2be5632c39af665450698c16ccc0f253b01f2c364296cba72488af4c0a35