Name:O365 New MFA Method Registered id:4e12db1f-f7c7-486d-8152-a221cad6ac2b version:11 date:None author:Mauricio Velazco, Splunk status:production type:TTP Description:The following analytic detects the registration of a new Multi-Factor Authentication (MFA) method for a user account within Office 365. It leverages O365 audit logs to identify changes in MFA configurations. This activity is significant as it may indicate an attacker's attempt to maintain persistence on a compromised account. If confirmed malicious, the attacker could bypass existing security measures, solidify their access, and potentially escalate privileges or access sensitive data. Immediate verification and remediation are required to secure the affected account. Data_source:
-O365 Update user.
search:`o365_management_activity` Workload=AzureActiveDirectory Operation="Update user." | eval propertyName = mvindex('ModifiedProperties{}.Name', 0) | search propertyName IN ("StrongAuthenticationMethod", "StrongAuthenticationPhoneAppDetail") | eval oldvalue = mvindex('ModifiedProperties{}.OldValue',0) | eval newvalue = mvindex('ModifiedProperties{}.NewValue',0) | rex field=newvalue max_match=0 "(?i)(?<new_method_type>MethodType|DeviceName)" | rex field=oldvalue max_match=0 "(?i)(?<old_method_type>MethodType|DeviceName)" | eval count_new_method_type = coalesce(mvcount(new_method_type), 0) | eval count_old_method_type = coalesce(mvcount(old_method_type), 0) | where count_new_method_type > count_old_method_type | fillnull | stats earliest(_time) as firstTime latest(_time) as lastTime values(propertyName) as propertyName by user newvalue oldvalue vendor_account vendor_product dest signature src | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_new_mfa_method_registered_filter`
how_to_implement:You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. known_false_positives:Users may register MFA methods legitimately, investigate and filter as needed. References: -https://attack.mitre.org/techniques/T1098/005/ -https://www.microsoft.com/en-us/security/blog/2023/06/08/detecting-and-mitigating-a-multi-stage-aitm-phishing-and-bec-campaign/ -https://www.csoonline.com/article/573451/sophisticated-bec-scammers-bypass-microsoft-365-multi-factor-authentication.html drilldown_searches: name:'View the detection results for - "$user$"' search:'%original_detection_search% | search user = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'7d' latest_offset:'0' analytic_story:['Office 365 Persistence Mechanisms']
