Techniques
Sample rules
Suspicious Rundll32 no Command Line Arguments
- source: splunk
- technicques:
- T1218.011
Description
The following analytic detects the execution of rundll32.exe without any command line arguments. This behavior is identified using Endpoint Detection and Response (EDR) telemetry, focusing on process execution logs. It is significant because rundll32.exe typically requires command line arguments to function properly, and its absence is often associated with malicious activities, such as those performed by Cobalt Strike. If confirmed malicious, this activity could indicate an attempt to execute arbitrary code, potentially leading to credential dumping, unauthorized file writes, or other malicious actions.
Detection logic
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where `process_rundll32` 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)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| regex process="(?i)(rundll32\.exe.{0,4}$)"
| `suspicious_rundll32_no_command_line_arguments_filter`
Rundll32 with no Command Line Arguments with Network
- source: splunk
- technicques:
- T1218.011
Description
The following analytic detects the execution of rundll32.exe without command line arguments, followed by a network connection. This behavior is identified using Endpoint Detection and Response (EDR) telemetry and network traffic data. It is significant because rundll32.exe typically requires arguments to function, and its absence is often associated with malicious activity, such as Cobalt Strike. If confirmed malicious, this activity could indicate an attempt to establish unauthorized network connections, potentially leading to data exfiltration or further compromise of the system.
Detection logic
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes where `process_rundll32` AND Processes.action!="blocked" by host _time span=1h Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| regex process="(?i)(rundll32\.exe.{0,4}$)"
| rename dest as src
| join host process_id [
| tstats `security_content_summariesonly` count FROM datamodel=Network_Traffic.All_Traffic where All_Traffic.dest_port != 0 by host All_Traffic.action All_Traffic.app All_Traffic.bytes All_Traffic.bytes_in All_Traffic.bytes_out All_Traffic.dest All_Traffic.dest_ip All_Traffic.dest_port 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.direction All_Traffic.process_id
| `drop_dm_object_name(All_Traffic)`]
| `rundll32_with_no_command_line_arguments_with_network_filter`