Name:Rundll32 with no Command Line Arguments with Network id:35307032-a12d-11eb-835f-acde48001122 version:10 date:2025-02-10 author:Steven Dick, Michael Haag, Splunk status:production type:TTP Description:The following analytic detects the execution of rundll32.exe without command line arguments, followed by a network connection. This behavior is identified using Endpoint Detection and Response (EDR) telemetry and network traffic data. It is significant because rundll32.exe typically requires arguments to function, and its absence is often associated with malicious activity, such as Cobalt Strike. If confirmed malicious, this activity could indicate an attempt to establish unauthorized network connections, potentially leading to data exfiltration or further compromise of the system. Data_source:
-Sysmon EventID 1 AND Sysmon EventID 3
search:| tstats prestats=t `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where `process_rundll32` AND Processes.action!="blocked" by Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product | `drop_dm_object_name(Processes)` | tstats prestats=t append=t `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Network_Traffic.All_Traffic where All_Traffic.dest_port != 0 by All_Traffic.action All_Traffic.app All_Traffic.dest All_Traffic.dest_ip All_Traffic.dest_port All_Traffic.direction All_Traffic.dvc All_Traffic.protocol All_Traffic.protocol_version All_Traffic.src All_Traffic.src_ip All_Traffic.src_port All_Traffic.transport All_Traffic.user All_Traffic.vendor_product All_Traffic.process_id | `drop_dm_object_name(All_Traffic)` | table action dest original_file_name parent_process parent_process_exec parent_process_guid parent_process_id parent_process_name parent_process_path process process_exec process_guid process_hash process_id process_integrity_level process_name process_path user user_id vendor_product app dest_ip dest_port direction dvc protocol protocol_version src src_ip src_port transport | stats values(action) as action values(dest) as dest values(original_file_name) as original_file_name values(parent_process) as parent_process values(parent_process_exec) as parent_process_exec values(parent_process_guid) as parent_process_guid values(parent_process_id) as parent_process_id values(parent_process_name) as parent_process_name values(parent_process_path) as parent_process_path values(process) as process values(process_exec) as process_exec values(process_hash) as process_hash values(process_guid) as process_guid values(process_integrity_level) as process_integrity_level values(process_name) as process_name values(process_path) as process_path values(user) as user values(user_id) as user_id values(vendor_product) as vendor_product values(app) as app values(dest_ip) as dest_ip values(dest_port) as dest_port values(direction) as direction values(dvc) as dvc values(protocol) as protocol values(protocol_version) as protocol_version values(src) as src values(src_ip) as src_ip values(src_port) as src_port values(transport) as transport by process_id | where isnotnull(process_name) AND isnotnull(dest_port) | `rundll32_with_no_command_line_arguments_with_network_filter`
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:Although unlikely, some legitimate applications may use a moved copy of rundll32, triggering a false positive. References: -https://attack.mitre.org/techniques/T1218/011/ -https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.011/T1218.011.md -https://lolbas-project.github.io/lolbas/Binaries/Rundll32/ -https://bohops.com/2018/02/26/leveraging-inf-sct-fetch-execute-techniques-for-bypass-evasion-persistence/ 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 ("$dest$") 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: - 'BlackSuit Ransomware' - 'Suspicious Rundll32 Activity' - 'Graceful Wipe Out Attack' - 'Cobalt Strike' - 'Compromised Windows Host' - 'PrintNightmare CVE-2021-34527' - 'BlackByte Ransomware' asset_type:Endpoint cve: - 'CVE-2021-34527' mitre_attack_id: - 'T1218.011' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' security_domain:endpoint
