IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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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:

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: 9 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 8.4.0

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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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)

Threat mapping

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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/

Rule version history

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Version 9 (8.4.0 release)

Formatting only

Version 7 (8.3.0 release)

Updated query, changed from:

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:success

Version 6 (8.1.0 release)

Updated query, changed from:

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

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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