- changed rule from esql to new_terms. While details are limited in telemetry, the noise is evident. We've also gotten complaints about the noise from our own infosec team, prompting this tuning. Changes to a new terms rule will reduce noise by over 90% when tested against prod data.
- This originally only triggered for role chaining within a single AWS account, so excluded common cross-account role assumption. However, I am unable to apply a filter for that with KQL but the benefits to creating new-terms rule outweigh the benefits of keeping that exclusion with esql.
- looks for unique combination of `aws.cloudtrail.user_identity.session_context.session_issuer.arn` (originating role) and `aws.cloudtrail.resources.arn`(target role). Because the only identity type we are concerned with here are `AssumedRole` types, we don't have the same new_terms field limitations as with other rules that also must consider `IAMUser` types. So these fields will suffice.
- added highlighted fields
- added index pattern. rule is compatible with filebeat
- updated the investigation guide and description and description
Note: I may consider creating a broader BBR rule, with the same criteria just not new terms, as a way of capturing all instances of role chaining for investigative purposes
Co-authored-by: Terrance DeJesus <99630311+terrancedejesus@users.noreply.github.com>
Isai
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