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Elastic Docs ›Elastic Security Solution [7.14] ›Detections and alerts ›Prebuilt rule reference

Attempts to Brute Force a Microsoft 365 User Account

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Attempts to Brute Force a Microsoft 365 User Account

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Identifies attempts to brute force a Microsoft 365 user account. An adversary may attempt a brute force attack to obtain unauthorized access to user accounts.

Rule type: threshold

Rule indices:

  • filebeat-*
  • logs-o365*

Severity: high

Risk score: 73

Runs every: 5 minutes

Searches indices from: now-30m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Cloud
  • Microsoft 365
  • Continuous Monitoring
  • SecOps
  • Identity and Access

Version: 5 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 7.14.0

Rule authors: Elastic, Willem D’Haese, Austin Songer

Rule license: Elastic License v2

Potential false positives

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Automated processes that attempt to authenticate using expired credentials and unbounded retries may lead to false positives.

Investigation guide

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Config

The Microsoft 365 Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.

Rule query

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event.dataset:o365.audit and event.provider:(AzureActiveDirectory or
Exchange) and event.category:authentication and
event.action:(UserLoginFailed or
PasswordLogonInitialAuthUsingPassword) and not
o365.audit.LogonError:(UserAccountNotFound or
EntitlementGrantsNotFound or UserStrongAuthEnrollmentRequired or
UserStrongAuthClientAuthNRequired or InvalidReplyTo) and
event.outcome:failure

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 5 (7.14.0 release)

  • Updated query, changed from:

    event.dataset:o365.audit and event.provider:AzureActiveDirectory and
event.category:authentication and event.action:UserLoginFailed and
event.outcome:failure
Version 3 (7.13.0 release)
  • Formatting only
Version 2 (7.12.0 release)
  • Formatting only
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