Detection: First time seen command line argument

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

Annotations

Default Configuration

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

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

• DHS Report TA18-074A

• Hidden Cobra Malware

• Orangeworm Attack Group

• Possible Backdoor Activity Associated With MUDCARP Espionage Campaigns

• Suspicious Command-Line Executions

Detection Testing

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