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How to Find Public AWS EC2 Instances

Exposing an EC2 directly to internet increases the attack surface and therefore the risk of compromise.

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_ec2_instance) and instance_public_ip_address!=null
    ​kind=aws_ec2_instance, ..., region=fixinventory-poweruser
    ​kind=aws_ec2_instance, ..., account=poweruser-team

  2. Pipe the search command into the dump command:

    > search is(aws_ec2_instance) and instance_public_ip_address!=null | dump
    ​reported:
    ​  id: /aws/ec2/123
    ​  name: some-name
    ​  ctime: '2022-12-05T22:53:14Z'
    ​  kind: aws_ec2_instance
    ​  age: 2mo28d

    The command output will list the details of all non-compliant aws_ec2_instance resources.

Remediation​

Use an ALB and apply WAF ACL.

note

Please refer to the AWS EC2 documentation for details.

Further Reading​