Name:Windows AD GPO New CSE Addition id:700c11d1-da09-47b2-81aa-358c143c7986 version:2 date:2024-09-30 author:Dean Luxton status:production type:TTP Description:This detection identifies when a a new client side extension is added to an Active Directory Group Policy using the Group Policy Management Console. Data_source:
-Windows Security 5136
search:`wineventlog_security` EventCode=5136 ObjectClass=groupPolicyContainer AttributeLDAPDisplayName=gPCMachineExtensionNames | stats min(_time) as _time values(eval(if(OperationType=="%%14675",AttributeValue,null))) as old_value values(eval(if(OperationType=="%%14674",AttributeValue,null))) as new_value values(OperationType) as OperationType by ObjectClass ObjectDN OpCorrelationID src_user SubjectLogonId | rex field=old_value max_match=10000 "(?P<old_values>\{.*?\})" | rex field=new_value max_match=10000 "(?P<new_values>\{.*?\})" | rex field=ObjectDN max_match=10000 "CN=(?P<policy_guid>\{.*?\})" | mvexpand new_values | where NOT new_values IN (old_values,"{00000000-0000-0000-0000-000000000000}",policy_guid) AND match(new_values, "^\{[A-Z|\d]+\-[A-Z|\d]+\-[A-Z|\d]+\-[A-Z|\d]+\-[A-Z|\d]+\}") | lookup msad_guid_lookup guid as new_values OUTPUTNEW displayName as policyType | eval newPolicy=if(policyType like "%",policyType,new_values) | join ObjectDN [| search `admon` objectCategory="CN=Group-Policy-Container*" admonEventType=Update | stats latest(displayName) as displayName by distinguishedName | eval ObjectDN=upper(distinguishedName)] | stats values(OpCorrelationID) as OpCorrelationID values(src_user) as src_user values(SubjectLogonId) as SubjectLogonId values(newPolicy) as newPolicy values(displayName) as policyName by ObjectDN | `windows_ad_gpo_new_cse_addition_filter`
how_to_implement:Ensure you are ingesting Active Directory audit logs - specifically event 5136, admon data is also used to display the display name of the GPO. See lantern article in references for further on how to onboard AD audit data. Ensure the wineventlog_security and admon macros are configured with the correct indexes. known_false_positives:General usage of group policy will trigger this detection, also please not GPOs modified using tools such as SharpGPOAbuse will not generate the AD audit events which enable this detection. References: -https://wald0.com/?p=179 -https://learn.microsoft.com/en-gb/archive/blogs/mempson/group-policy-client-side-extension-list -https://lantern.splunk.com/Security/Product_Tips/Enterprise_Security/Enabling_an_audit_trail_from_Active_Directory -https://github.com/FSecureLABS/SharpGPOAbuse drilldown_searches: name:'View the detection results for - "$src_user$"' search:'%original_detection_search% | search src_user = "$src_user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$src_user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src_user$") starthoursago=168 | 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:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'Sneaky Active Directory Persistence Tricks' asset_type:Endpoint confidence:100 impact:100 message:$src_user$ has added new GPO Client Side Extensions $newPolicy$ to the policy $policyName$ mitre_attack_id: - 'T1484' - 'T1484.001' - 'T1222' - 'T1222.001' observable: name:'src_user' type:'User' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' risk_score:100 required_fields: - '_time' - 'OperationType' - 'ObjectDN' - 'OpCorrelationID' - 'src_user' - 'AttributeLDAPDisplayName' - 'AttributeValue' - 'ObjectClass' - 'SubjectLogonId' - 'DSName' security_domain:endpoint
