Attempts to Brute Force a Microsoft 365 User Account

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: 5m

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

Maximum alerts per execution: 100

References:

https://blueteamblog.com/7-ways-to-monitor-your-office-365-logs-using-siem

Tags:

Elastic
Cloud
Microsoft 365
Continuous Monitoring
SecOps
Identity and Access

Version: 5

Rule authors:

Elastic
Willem D’Haese
Austin Songer

Rule license: Elastic License v2

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

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
Technique:
- Name: Brute Force
- ID: T1110
- Reference URL: https://attack.mitre.org/techniques/T1110/

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