Unusually Long Command Line

SPLUNK detection rule by David Dorsey, Splunk · Apache-2.0

The following analytic detects unusually long command lines, which may indicate malicious activity. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on the length of command lines executed on hosts. This behavior is significant because attackers often use obfuscated or complex command lines to evade detection and execute malicious payloads. If confirmed malicious, this activity could lead to data theft, ransomware deployment, or further system compromise. Analysts should investigate the source and content of the command line, inspect relevant artifacts, and review concurrent processes to identify potential threats.

name: Unusually Long Command Line
id: c77162d3-f93c-45cc-80c8-22f6a4264e7f
version: 14
creation_date: '2020-04-29'
modification_date: '2026-05-13'
author: David Dorsey, Splunk
status: experimental
type: Anomaly
description: The following analytic detects unusually long command lines, which may indicate malicious activity. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on the length of command lines executed on hosts. This behavior is significant because attackers often use obfuscated or complex command lines to evade detection and execute malicious payloads. If confirmed malicious, this activity could lead to data theft, ransomware deployment, or further system compromise. Analysts should investigate the source and content of the command line, inspect relevant artifacts, and review concurrent processes to identify potential threats.
data_source:
    - Sysmon EventID 1
    - Windows Event Log Security 4688
    - CrowdStrike ProcessRollup2
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      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)`
    | eval processlen=len(process)
    | eventstats stdev(processlen) as stdev, avg(processlen) as avg
      BY dest
    | stats max(processlen) as maxlen, values(stdev) as stdevperhost, values(avg) as avgperhost
      BY dest, user, process_name,
         process
    | eval threshold = 3
    | where maxlen > ((threshold*stdevperhost) + avgperhost)
    | `unusually_long_command_line_filter`
how_to_implement: 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: Some legitimate applications start with long command lines.
references: []
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: Unusually long command line $process_name$ on $dest$
threat_objects:
    - field: process_name
      type: process_name
analytic_story:
    - Suspicious Command-Line Executions
    - Unusual Processes
    - Possible Backdoor Activity Associated With MUDCARP Espionage Campaigns
    - Ransomware
asset_type: Endpoint
mitre_attack_id: []
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint

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83528827-0418-419e-84be-b2cb3de76406

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