Detection: Linux File Creation In System Generator Directory

Updated Date: 2026-07-08 ID: 06c23568-e05b-4fff-95cd-8b0303b6d032 Author: Raven Tait, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6from datamodel=Endpoint.Filesystem where
 7
 8Filesystem.action IN ("created", "modified")
 9Filesystem.file_path="*/lib/systemd/system-generators/*"
10
11by Filesystem.file_path Filesystem.file_name Filesystem.user Filesystem.dest
12   Filesystem.action Filesystem.process_guid Filesystem.process_id
13
14
15| `drop_dm_object_name(Filesystem)`
16
17| `security_content_ctime(firstTime)`
18
19| `security_content_ctime(lastTime)`
20
21| `linux_file_creation_in_system_generator_directory_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon for Linux EventID 11	Linux	`'sysmon:linux'`	`'Syslog:Linux-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
linux_file_creation_in_system_generator_directory_filter	`search *`

linux_file_creation_in_system_generator_directory_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
T1037.005	Startup Items	Persistence
T1547	Boot or Logon Autostart Execution	Privilege Escalation

Exploitation

Installation

DE.AE

CIS 10

Default Configuration

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

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Finding (Notable)	No
Creates Intermediate Finding (Risk Event)	Yes

Anomaly detections generate Intermediate Findings (Risk Events). They do not generate a Finding (Notable) directly.

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 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.

Associated Analytic Story

Linux Persistence Techniques

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
The file [$file_name$] was created in the system generator directory [$file_path$] on [$dest$] by [$user$].	dest	system	20

Threat Objects

Field	Type
file_name	file_name

References

https://github.com/Aegrah/PANIX

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`
Integration	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`

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: 1