Detection: First time seen command line argument

REMOVED DETECTION

This detection has been removed from the Splunk Threat Research content library and is no longer maintained or supported.

Reason: Detection deprecated as it no longer effectively identifies the intended malicious activity

Removed in version: 5.2.0

If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2026-05-13 ID: a1b6e73f-98d5-470f-99ac-77aacd578473 Author: Bhavin Patel, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

This search looks for command-line arguments that use a /c parameter to execute a command that has not previously been seen.

Search

 1
 2| tstats `security_content_summariesonly` min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name = cmd.exe Processes.process = "* /c *" by Processes.process Processes.process_name Processes.parent_process_name Processes.dest
 3| `drop_dm_object_name(Processes)`
 4| `security_content_ctime(firstTime)` 
 5| `security_content_ctime(lastTime)` 
 6| search [
 7| tstats `security_content_summariesonly` earliest(_time) as firstTime latest(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name = cmd.exe Processes.process = "* /c *" by Processes.process 
 8| `drop_dm_object_name(Processes)` 
 9| inputlookup append=t previously_seen_cmd_line_arguments 
10| stats min(firstTime) as firstTime, max(lastTime) as lastTime by process 
11| outputlookup previously_seen_cmd_line_arguments 
12| eval newCmdLineArgument=if(firstTime >= relative_time(now(), "-70m@m"), 1, 0) 
13| where newCmdLineArgument=1 
14| `security_content_ctime(firstTime)` 
15| `security_content_ctime(lastTime)` 
16| table process] 
17| `first_time_seen_command_line_argument_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 1	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_summariesonly	`summariesonly=`summariesonly_config `allow_old_summaries=`oldsummaries_config `fillnull_value=`fillnull_config``
first_time_seen_command_line_argument_filter	``

first_time_seen_command_line_argument_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1059.001	PowerShell	Execution
T1059.003	Windows Command Shell	Execution

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`N/A`
Earliest Time	`N/A`
Latest Time	`N/A`
Schedule Window	`N/A`
Creates Finding (Notable)	No
Creates Intermediate Finding (Risk Event)	No

Hunting detections do not generate a Finding (Notable) or Intermediate Findings (Risk Events).

Implementation

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

Legitimate programs can also use command-line arguments to execute. Please verify the command-line arguments to check what command/program is being executed. We recommend customizing the first_time_seen_cmd_line_filter macro to exclude legitimate parent_process_name

Associated Analytic Story

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	Not Applicable	N/A	`N/A`	`N/A`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub |

Version: 8