[New Rule] Multiple Microsoft 365 User Account Lockouts in Short Time Window

[terrancedejesus]

Pull Request

Issue link(s):

• [Rule Tuning] Potential Password Spraying of Microsoft 365 User Accounts #3934

Summary - What I changed

Adds detection coverage for a burst of account lockouts related to M365 users. This is often the result of generic brute-force attempts or credential stuffing. Adversaries with stolen or brokered credentials may programmatically check which are valid by hitting MSFT's login endpoint with ROPC auth workflows to determine which credentials are valid causing lockouts.

Query contains the following logic:

• Scoped to M365 Audit Logs
• Truncates a time window of 5 minutes (300 seconds)
• normalizes the fields of interest
• focuses on authentication logs for AAD or Exchange, specifically failed logins
• auth workflows can be OAuth or OWA
• filters specifically on IdsLocked where are response codes if auth to an account is attempted but its already locked
• Focuses on user principals, ignoring service and system accounts
• Ignores if the source is MSFT ASN
• leverages stats to ensure >= 10 unique users within 5 minutes

How To Test

• The query can be used in TRADE's serverless stack to test syntax and review hits.

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?

[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.