first ↗

Use the first() function to retrieve the first chronologically recorded value of a specified field within a grouped set of records.

Syntax

first(<field>)

Parameters

Name Type Required Description
field any Yes The field from which to extract the first recorded value based on chronological order.

Returns

The first() function returns the value of the specified field from the oldest event in the evaluated group. The data type of the returned value matches the data type of the input field.

Usage Notes

  • The first() function is an aggregate function and must be used within the comp stage.
  • The chronological order of the records is determined by the underlying time field (such as _time) associated with the data events.
  • If the first record contains a NULL value for the evaluated field, the function will return NULL.
  • This function is frequently used in threat hunting to identify the initial occurrence of an artifact or behavior, such as the first command executed in a session or the initial process started by a specific user.

Examples

Example 1: Identify the First Process Executed per Host

Goal: Find the first recorded process name that was executed on each endpoint within the queried time frame.

XQL Code:

config timeframe = 1d  
| dataset = xdr_data  
| filter action_process_image_name != null  
| comp first(action_process_image_name) as first_process by agent_hostname  
| fields agent_hostname, first_process  
| limit 3

Explanation: You use the comp stage to group the events by agent_hostname. For each unique host, the first() function evaluates the timeline of the records and returns the action_process_image_name associated with the chronologically oldest event in that group. The result is assigned to the first_process alias.

Output:

AGENT_HOSTNAME FIRST_PROCESS
endpoint-win-01 C:\Windows\System32\smss.exe
endpoint-mac-02 /sbin/launchd
srv-linux-03 /usr/lib/systemd/systemd

Example 2: Retrieve the First Command Line for a Process

Goal: Identify the first command line argument used to execute a specific process across your environment.

XQL Code:

config timeframe = 1d  
| dataset = xdr_data  
| filter action_process_image_name = "powershell.exe"  
| comp first(action_process_image_command_line) as initial_cmd by agent_hostname  
| fields agent_hostname, initial_cmd  
| limit 2

Explanation: This query filters for execution events involving powershell.exe. Using the comp stage, it groups the results by agent_hostname and uses the first() function to extract the chronologically first command line argument executed by PowerShell on that host.

Output:

AGENT_HOSTNAME INITIAL_CMD
endpoint-win-01 powershell.exe -ExecutionPolicy Bypass -File C:\scripts\setup.ps1
srv-win-02 "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -NoProfile