[New Rule] Microsoft Defender XDR Promotion Rules

[terrancedejesus]

Pull Request

Issue link(s):

Summary - What I changed

Reported duplicate open Elastic alerts for the same Defender alert/incident when using a copy of the generic External Alerts rule with suppression on event.id. Investigation of the integration ingest pipelines showed event.id is already the stable Defender ID, so the duplicates come from suppression lifecycle behavior, not a wrong key. There was no out-of-the-box rule for the native m365_defender.alert and incident data streams, similar to CrowdStrike, S1, etc.. These rules give a turnkey workflow that keeps one analyst-facing alert per Defender alert or incident and folds subsequent update events into it, with the suppression key and window set correctly and documented.

New files (2 promotion rules in rules/promotions/):

• m365_defender_alert_external_alerts.toml: promotes each Microsoft Defender XDR alert from logs-m365_defender.alert-* into an Elastic alert. Suppresses on m365_defender.alert.id + tenant_id with a 1 day window.
• m365_defender_incident_external_alerts.toml: promotes each Defender incident from logs-m365_defender.incident-*. Suppresses on m365_defender.incident.id + tenant_id with a 1 day window. This is the recommended default since it produces one Elastic alert per incident.

Modified files (2):

• rules_building_block/initial_access_microsoft_defender_alerts_signal.toml: added a note pointing to the two new promotion rule IDs (clarifying UAL path vs native data stream), and raised severity from low to medium (risk_score 21 to 47).

Checklist

• Added a label for the type of pr: bug, enhancement, schema, maintenance, Rule: New, Rule: Deprecation, Rule: Tuning, Hunt: New, or Hunt: Tuning so guidelines can be generated
• Added the meta:rapid-merge label if planning to merge within 24 hours
• Secret and sensitive material has been managed correctly
• Automated testing was updated or added to match the most common scenarios
• Documentation and comments were added for features that require explanation

Contributor checklist

• Have you signed the contributor license agreement?
• Have you followed the contributor guidelines?

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Microsoft Defender XDR Incident External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta
• ❌ Microsoft Defender XDR Alert External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta
• ❌ External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[github-actions]

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.

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Microsoft Defender XDR Incident External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta
• ❌ Microsoft Defender XDR Alert External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Microsoft Defender XDR Incident External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta
• ❌ Microsoft Defender XDR Alert External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ Microsoft Defender XDR Incident External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta
• ❌ Microsoft Defender XDR Alert External Alerts (kuery)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[Copilot]

Pull request overview

Adds Microsoft Defender XDR “promotion” rules so native m365_defender.alert and m365_defender.incident data streams can be promoted into Elastic detection alerts with suppression keyed on stable Defender IDs, enabling a single ongoing Elastic alert per Defender alert/incident update lifecycle.

Changes:

• Introduces dedicated promotion rules for Defender XDR alerts and incidents (with 24h suppression windows keyed on {alert|incident}.id + tenant_id).
• Updates the existing UAL-based “M365 Defender Alerts Signal” building block rule name/description and adds guidance pointing to the new promotion rules.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
rules/promotions/m365_defender_incident_external_alerts.toml	New incident-level promotion rule with suppression keyed on incident id + tenant id and an investigation guide.
rules/promotions/m365_defender_alert_external_alerts.toml	New alert-level promotion rule with suppression keyed on alert id + tenant id and an investigation guide.
rules_building_block/initial_access_microsoft_defender_alerts_signal.toml	Clarifies this building block is UAL-specific via naming + note, and updates metadata/severity fields.