Name:Windows Rundll32 Apply User Settings Changes id:b9fb8d97-dbc9-4a09-804c-ff0e3862bb2d version:13 date:None author:Teoderick Contreras, Nasreddine Bencherchali, Splunk status:production type:Anomaly Description:The following analytic detects the execution of rundll32 with a call to the user32 DLL, specifically the UpdatePerUserSystemParameters function.
This function is responsible for updating system parameters, such as desktop backgrounds, display settings, and visual themes.
It leverages data from Endpoint Detection and Response (EDR) agents, focusing on command-line executions.
This activity can be significant as it is an uncommon way to apply settings. It was also observed as part of Rhysida Ransomware activity.
If confirmed malicious, this could allow an attacker to disguise activities or make unauthorized system changes, potentially leading to persistent unauthorized access.
Data_source:
-Sysmon EventID 1
-Windows Event Log Security 4688
-CrowdStrike ProcessRollup2
search:| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
how_to_implement:The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process. known_false_positives:No false positives have been identified at this time. References: -https://www.cisa.gov/news-events/cybersecurity-advisories/aa23-319a -https://www.cisa.gov/sites/default/files/publications/aa22-264a-iranian-cyber-actors-conduct-cyber-operations-against-the-government-of-albania.pdf -https://cdn.pathfactory.com/assets/10555/contents/400686/13f4424c-05b4-46db-bb9c-6bf9b5436ec4.pdf drilldown_searches: name:'View the detection results for - "$dest$"' search:'%original_detection_search% | search dest = "$dest$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$dest$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | 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:['Rhysida Ransomware']
