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Remove superfluous stats field
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danbutcher-payroc committed Oct 31, 2024
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Expand Up @@ -8,7 +8,7 @@ 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 *, 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`'
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(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 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:
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