* [Rule Tuning] SSM Session Started to EC2 Instance
Role/role session noise seen in telemetry due to new fields term using `aws.cloudtrail.user_identity.arn`, which is unique for each role session and does not isolate the role itself.
- new fields term change to `cloud.account.id` and `user.name` combination to account for both IAMUsers and Roles across multiple accounts.
- added AWS to the rule name
- reduced execution window
- small edits to description and IG
- added reference from IG to Reference section
* adding highlighted fields
* added EC2 tag
* Update lateral_movement_aws_ssm_start_session_to_ec2_instance.toml
* Apply suggestions from code review
* [Rule Tunings] AWS Route Table Created / AWS EC2 Route Table Modified or Deleted
AWS Route Table Created
- turned this into a new_terms rule to reduce noise and be more indicative of potential malicious behavior. Used `cloud.account.id`, `user.name` combination to account for both roles and users doing this behavior for the first time.
- changed execution interval
- changed the name to add EC2
- slight adjustments to IG and description
- fixed tagging error
- added investigation fields
AWS EC2 Route Table Modified or Deleted
- replaced new terms field to `cloud.account.id`, `user.name` combination to account for both roles and users doing this behavior for the first time.
- removed the exclusions from this rule. These exclusions, while meant to reduce noise caused by automation tools, actually just provide an easy bypass. A user can simply use CloudFormation to perform the exact same behaviors and avoid detection. I've shown this in the screenshot below, I ran a nearly identical script, one with and one without using CloudFormation. While `source.address` is `cloudformation.amazonaws.com` the behavior was still performed by an IAMUser and should still be evaluated. The fact that this is a new terms rule will reduce the risk of noise due to automation using these tools.
- changed execution interval
- slight adjustments to IG and description
- added investigation fields
* Update persistence_route_table_created.toml
* Update rules/integrations/aws/persistence_ec2_route_table_modified_or_deleted.toml
- query change : I chose to replace `aws.cloudtrail.user_identity.arn` with `user.id` and a more accurate wildcard pattern. This will reduce the chances of this rule triggering for role sessions outside of those started by EC2 instances. The wildcard pattern looks for a role session name that starts with `i-` this is because when an EC2 instance operates using it's attached Role (instance profile), the session name attached to that role name is the instance id (`i-......`). The `user.id` field appends this session name to the role name via a standard pattern `:[session_name]`, making it a more reliable field to use in this case.
- small edits to description and IG
- reduced execution window
- reduced history window
- edited highlighted fields
Note: the new_terms field here remains `aws.cloudtrail.user_identity.arn` because we are only interested in assumed roles, and even more particular, only those used by an EC2 instance. This means we want to evaluate each individual instance's behavior rather than the broader behavior of the role itself. The arn field will capture each instance id (session name) alongside the role itself.
* adding new rule 'Threat Intelligence Signal - Microsoft Defender for Office 365'
* added mitre mapping
* Update rules/integrations/o365/initial_access_defender_for_m365_threat_intelligence_signal.toml
Co-authored-by: Isai <59296946+imays11@users.noreply.github.com>
* added note for max signals
* linted
* fixed unit test failure
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Co-authored-by: Isai <59296946+imays11@users.noreply.github.com>
* tuning rule 'Multi-Factor Authentication Disabled for User'
* adjusted query logic
* fixed query logic for optimization that passes unit tests; changed severity and risk back to medium
Rule is executing as expected, however it is alerting on failed requests. Low alert telemetry.
This tuning:
- removed markdown and edited description to be more specific
- reduced execution window for 1 min lookback
- name change to add `AWS` consistent with all other rules
- added references that reflect in the wild threats and persistence usage
- increased risk_score and severity to medium accounting for usage as persistence mechanism in the wild
- added Persistence tag and Mitre tactic, technique, subtechnique
- added `event.outcome: success` criteria to query
- edited investigation guide to be more accurate reflection of steps required for investigating alert, including appropriate response action
- added highlighted fields
** Note: only IAMUser and Root user identities can call this actions so we can use `aws.cloudtrail.user_identity.arn` as the new terms field without worrying about Role vs Role + Session issue seen with other new_terms rules
* [Tuning] First Time AWS Cloudformation Stack Creation by User
- corrected a creation_date error
- Removed `CreateStackSet` API call as this only creates a blueprint for creating stack instances across multiple AWS accounts and regions but does not actually create the resources
- Added `CreateStackInstances` API call which is used to create resources defined in the StackSet
- removed user from rule name as this also triggers for roles
- edited description and investigation guide
- added Mitre technique
* adding highlighted fields
This rule is evaluating the "new terms" against every individual role session, rather than against the Role itself. This is causing a massive volume of alerts
- updated rule description and investigation guide
- reduced execution window and interval
- replaced new terms from `user.id` to combination of `cloud.account.id` and `user.name` to account for evaluation against Roles and in the event that separate AWS accounts under the same Org reuse IAM user names. This will only evaluate the Role instead of each individual role session, which should greatly improve performance.
* [Rule Tuning] AWS STS GetCallerIdentity API Called for the First Time
Rule is executing as expected with no troubling alerts in telemetry. For tuning I've:
- reduced the execution window
- removed MD from description and FP as it's not supported in Kibana UI
- edited some of the language of IG to speak about the exclusion of AssumedRoles
- edited the highlighted fields for consistency across AWS rules
* updated broken link
updated broken reference link
Isai