Name:Windows New Custom Security Descriptor Set On EventLog Channel id:c0e5dd5a-2117-41d5-a04c-82a762a86a38 version:1 date:2024-12-06 author:Nasreddine Bencherchali, Michael Haag, Splunk status:production type:Anomaly Description:The following analytic detects suspicious modifications to the EventLog security descriptor registry value for defense evasion. It leverages data from the Endpoint.Registry data model, focusing on changes to the "CustomSD" value within the "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Eventlog\<Channel>\CustomSD" path. This activity is significant as changes to the access permissions of the event log could blind security products and help attackers evade defenses. If confirmed malicious, this could allow attackers to block users and security products from viewing, ingesting and interacting event logs. Data_source:
-Sysmon EventID 13
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Registry WHERE Registry.registry_path= "*\\Services\\Eventlog\\*" AND Registry.registry_value_name=CustomSD BY Registry.dest Registry.registry_value_data Registry.action Registry.process_guid Registry.process_id Registry.registry_key_name Registry.user Registry.registry_value_name | `drop_dm_object_name(Registry)` | where isnotnull(registry_value_data) | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_new_custom_security_descriptor_set_on_eventlog_channel_filter`
how_to_implement:To successfully implement this search, you must be ingesting data that records registry activity from your hosts to populate the endpoint data model in the registry node. This is typically populated via endpoint detection-and-response product, such as Carbon Black or endpoint data sources, such as Sysmon. The data used for this search is typically generated via logs that report reads and writes to the registry. If you are using Sysmon, you must have at least version 2.0 of the official Sysmon TA. https://splunkbase.splunk.com/app/5709 known_false_positives:None identified, setting up the "CustomSD" value is considered a legacy option and shouldn't be a common activity. References: -https://learn.microsoft.com/en-us/troubleshoot/windows-server/group-policy/set-event-log-security-locally-or-via-group-policy -https://attack.mitre.org/techniques/T1562/002/ drilldown_searches: name:'View the detection results for - "$dest$" and "$user$"' search:'%original_detection_search% | search dest = "$dest$" user = "$user$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$" and "$user$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$", "$user$") 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: - 'LockBit Ransomware' - 'Defense Evasion or Unauthorized Access Via SDDL Tampering' asset_type:Endpoint confidence:80 impact:80 message:modified/added/deleted registry entry $registry_path$ in $dest$ mitre_attack_id: - 'T1562.002' observable: name:'dest' type:'Hostname' - role: - 'Victim' name:'user' type:'User' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'Registry.dest' - 'Registry.registry_value_name' - 'Registry.registry_key_name' - 'Registry.registry_path' - 'Registry.registry_value_data' - 'Registry.process_guid' risk_score:64 security_domain:endpoint
