Skip to main content

How to Find AWS CloudTrail Trails Missing Alarms for Network ACL Changes

Monitoring unauthorized API calls will help reveal application errors and may reduce time to detect malicious activity.

info

This security check is part of the CIS Amazon Web Services Benchmarks and is rated severity medium.

Prerequisites​

This guide assumes that you have already installed and configured Fix Inventory to collect your AWS resources.

Directions​

  1. Execute the following search command in Fix Inventory Shell:

    > search is(aws_cloud_trail) and trail_is_multi_region_trail=true and trail_status.is_logging=true with(empty, --> is(aws_cloudwatch_log_group) with(any, --> is(aws_cloudwatch_metric_filter) and filter_pattern~"\s*\$\.eventName\s*=\s*CreateNetworkAcl.+\$\.eventName\s*=\s*CreateNetworkAclEntry.+\$\.eventName\s*=\s*DeleteNetworkAcl.+\$\.eventName\s*=\s*DeleteNetworkAclEntry.+\$\.eventName\s*=\s*ReplaceNetworkAclEntry.+\$\.eventName\s*=\s*ReplaceNetworkAclAssociation"))
    ​kind=aws_cloud_trail, ..., region=fixinventory-poweruser
    ​kind=aws_cloud_trail, ..., account=poweruser-team

  2. Pipe the search command into the dump command:

    > search is(aws_cloud_trail) and trail_is_multi_region_trail=true and trail_status.is_logging=true with(empty, --> is(aws_cloudwatch_log_group) with(any, --> is(aws_cloudwatch_metric_filter) and filter_pattern~"\s*\$\.eventName\s*=\s*CreateNetworkAcl.+\$\.eventName\s*=\s*CreateNetworkAclEntry.+\$\.eventName\s*=\s*DeleteNetworkAcl.+\$\.eventName\s*=\s*DeleteNetworkAclEntry.+\$\.eventName\s*=\s*ReplaceNetworkAclEntry.+\$\.eventName\s*=\s*ReplaceNetworkAclAssociation")) | dump
    ​reported:
    ​  id: /aws/cloudtrail/123
    ​  name: some-name
    ​  ctime: '2022-12-05T22:53:14Z'
    ​  kind: aws_cloud_trail
    ​  age: 2mo28d

    The command output will list the details of all non-compliant aws_cloud_trail resources.

Remediation​

It is recommended that a metric filter and alarm be established for Network ACL changes.

note

Please refer to the AWS CloudTrail documentation for details.

Further Reading​