Spoolsv Spawning Rundll32
Description
The following analytic detects the spawning of rundll32.exe without command-line arguments by spoolsv.exe, which is unusual and potentially indicative of exploitation attempts like CVE-2021-34527 (PrintNightmare). This detection leverages Endpoint Detection and Response (EDR) telemetry, focusing on process creation events where spoolsv.exe is the parent process. This activity is significant as spoolsv.exe typically does not spawn other processes, and such behavior could indicate an active exploitation attempt. If confirmed malicious, this could allow an attacker to execute arbitrary code, escalate privileges, or maintain persistence on the compromised endpoint.
Query · spl
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
WHERE Processes.parent_process_name=spoolsv.exe `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)`
| `spoolsv_spawning_rundll32_filter`
Implementation guide
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
- Limited false positives have been identified. There are limited instances where `rundll32.exe` may be spawned by a legitimate print driver.
Analyst notes
Known false positives: Limited false positives have been identified. There are limited instances where rundll32.exe may be spawned by a legitimate print driver.