Update search

detections/cloud/azure_ad_authentication_failed_during_mfa_challenge.yml

@@ -1,20 +1,21 @@
 name: Azure AD Authentication Failed During MFA Challenge
 id: e62c9c2e-bf51-4719-906c-3074618fcc1c
-version: 5
-date: '2024-09-30'
-author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk
+version: 6
+date: '2024-10-31'
+author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk, 0xC0FFEEEE
 status: production
 type: TTP
 description: The following analytic identifies failed authentication attempts against an Azure AD tenant during the Multi-Factor Authentication (MFA) challenge, specifically flagged by error code 500121. It leverages Azure AD SignInLogs to detect these events. This activity is significant as it may indicate an adversary attempting to authenticate using compromised credentials on an account with MFA enabled. If confirmed malicious, this could suggest an ongoing effort to bypass MFA protections, potentially leading to unauthorized access and further compromise of the affected account.
 data_source:
 - Azure Active Directory
-search: '`azure_monitor_aad` category=SignInLogs properties.status.errorCode=500121 | rename properties.* as * | stats count min(_time) as firstTime max(_time) as lastTime by user, src_ip, status.additionalDetails, appDisplayName, user_agent | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `azure_ad_authentication_failed_during_mfa_challenge_filter`'
+search: '`azure_monitor_aad` category=SignInLogs properties.status.errorCode=500121 | rename properties.* as *, authenticationDetails{}.* as * | eval time=strptime(authenticationStepDateTime, "%Y-%m-%dT%H:%M:%S") | eval auth_detail=mvzip(strftime(time, "%Y-%m-%dT%H:%M:%S"),authenticationStepResultDetail," - "), auth_msg=mvappend(''status.additionalDetails'', authenticationStepResultDetail) | eval auth_method=mvmap(authenticationMethod, if(isnull(mvfind(''mfaDetail.authMethod'', authenticationMethod)), authenticationMethod, null())) | stats min(_time) as firstTime, max(_time) as lastTime, values(user) as user, values(src_ip) as src_ip, values(mfaDetail.authMethod) as mfa_method, values(auth_method) as auth_method, values(auth_detail) as auth_detail, values(status.additionalDetails) as status.additionalDetails, values(auth_msg) as auth_msg, values(appDisplayName) as appDisplayName, values(user_agent) as user_agent by tenantId originalRequestId | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | search NOT auth_msg="MFA successfully completed" | sort 0 - firstTime | `azure_ad_authentication_failed_during_mfa_challenge_filter`'
 how_to_implement: You must install the latest version of Splunk Add-on for Microsoft Cloud Services from Splunkbase (https://splunkbase.splunk.com/app/3110/#/details). You must be ingesting Azure Active Directory events into your Splunk environment through an EventHub. This analytic was written to be used with the azure:monitor:aad sourcetype leveraging the SignInLogs log category.
-known_false_positives: Legitimate users may miss to reply the MFA challenge within the time window or deny it by mistake.
+known_false_positives: Legitimate users may generate MFA failures by selecting alternate MFA methods, or by either; failing to reply the MFA challenge within the time window or dening it by mistake.
 references:
 - https://attack.mitre.org/techniques/T1621/
 - https://attack.mitre.org/techniques/T1078/004/
 - https://docs.microsoft.com/en-us/azure/active-directory/authentication/concept-mfa-howitworks
+- https://learn.microsoft.com/en-us/entra/identity/monitoring-health/concept-sign-in-log-activity-details
 drilldown_searches:
 - name: View the detection results for - "$user$"
   search: '%original_detection_search% | search  user = "$user$"'