[New Rule] AWS EC2 Instance Interaction with IAM Service

Issue link(s):

https://github.com/elastic/ia-trade-team/issues/346

Summary - What I changed

Identifies when an EC2 instance interacts with the AWS IAM service via an assumed role. This is uncommon behavior and could indicate an attacker using compromised creadentials to further exploit an environment. For example, an assumed role could be used to create new users for persistence or add permissions for privilege escalation. An EC2 instance assumes a role using their EC2 id as the session name. This rule looks for the pattern "i-" which is the beginning pattern for assumed role sessions started by an EC2 instance.

I chose to use the user.id field over the aws.cloudtrail.user_identity.arn because this field is able to be ingested via telemtry as PII has been stripped but the session name necessary to identify the identity as an EC2 instance is still included

Rule: New - Guidelines

These guidelines serve as a reminder set of considerations when proposing a new rule.

Documentation and Context

[ ] Detailed description of the rule.
[ ] List any new fields required in ECS/data sources.
[ ] Link related issues or PRs.
[ ] Include references.

Rule Metadata Checks

[ ] creation_date matches the date of creation PR initially merged.
[ ] min_stack_version should support the widest stack versions.
[ ] name and description should be descriptive and not include typos.
[ ] query should be inclusive, not overly exclusive, considering performance for diverse environments. Non ecs fields should be added to non-ecs-schema.json if not available in an integration.
[ ] min_stack_comments and min_stack_version should be included if the rule is only compatible starting from a specific stack version.
[ ] index pattern should be neither too specific nor too vague, ensuring it accurately matches the relevant data stream (e.g., use logs-endpoint.process-* for process data).
[ ] integration should align with the index. If the integration is newly introduced, ensure the manifest, schemas, and new_rule.yaml template are updated.
[ ] setup should include the necessary steps to configure the integration.
[ ] note should include any additional information (e.g. Triage and analysis investigation guides, timeline templates).
[ ] tags should be relevant to the threat and align/added to the EXPECTED_RULE_TAGS in the definitions.py file.
[ ] threat, techniques, and subtechniques should map to ATT&CK always if possible.

New BBR Rules

[ ] building_block_type should be included if the rule is a building block and the rule should be located in the rules_building_block folder.
[ ] bypass_bbr_timing should be included if adding custom lookback timing to the rule.

Testing and Validation

[ ] Provide evidence of testing and detecting the expected threat.
[ ] Check for existence of coverage to prevent duplication.

elastic / detection-rules