Linux File Creation In System Generator Directory

SPLUNK detection rule by Raven Tait, Splunk · Apache-2.0

The following analytic detects potential persistence using a systemd generator on Linux, which involves creating a malicious script or binary that is typically executed during the system's boot process. Systemd generators are typically placed in directories like /lib/systemd/system-generators/, where they are run early in the boot sequence to dynamically generate or modify unit files that control system services. By placing a custom generator in this directory, an attacker can ensure their code is executed each time the system starts, allowing them to maintain access or control even after reboots.

name: Linux File Creation In System Generator Directory
id: 06c23568-e05b-4fff-95cd-8b0303b6d032
version: 1
creation_date: '2026-07-08'
modification_date: '2026-07-08'
author: Raven Tait, Splunk
status: production
type: Anomaly
description: |-
    The following analytic detects potential persistence using a systemd generator on Linux, which involves creating a malicious script or binary that is typically executed during the system's boot process.
    Systemd generators are typically placed in directories like /lib/systemd/system-generators/, where they are run early in the boot sequence to dynamically generate or modify unit files that control system services.
    By placing a custom generator in this directory, an attacker can ensure their code is executed each time the system starts, allowing them to maintain access or control even after reboots.
data_source:
    - Sysmon for Linux EventID 11
search: |-
    | tstats `security_content_summariesonly`
      count min(_time) as firstTime
            max(_time) as lastTime

    from datamodel=Endpoint.Filesystem where

    Filesystem.action IN ("created", "modified")
    Filesystem.file_path="*/lib/systemd/system-generators/*"

    by Filesystem.file_path Filesystem.file_name Filesystem.user Filesystem.dest
       Filesystem.action Filesystem.process_guid Filesystem.process_id

    | `drop_dm_object_name(Filesystem)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `linux_file_creation_in_system_generator_directory_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 file creation events including the file path and user context. 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 `Filesystem` 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 system administrators or software packages may place custom generators in systemd generator directories during system configuration or application deployment. Filter based on known software installations and verified administrative activity.
references:
    - https://github.com/Aegrah/PANIX
drilldown_searches:
    - earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
      name: View the detection results for - "$user$" and "$dest$"
      search: '%original_detection_search% | search  user = "$user$" dest = "$dest$"'
    - name: View risk events for the last 7 days for - "$user$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: '0'
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: The file [$file_name$] was created in the system generator directory [$file_path$] on [$dest$] by [$user$].
threat_objects:
    - field: file_name
      type: file_name
analytic_story:
    - Linux Persistence Techniques
asset_type: Endpoint
mitre_attack_id:
    - T1037.005
    - T1547
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      test_type: unit
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1037.005/linux_persistence_via_system_generator/snapattack_linux.log
          source: Syslog:Linux-Sysmon/Operational
          sourcetype: sysmon:linux

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