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Description

The following analytic detects the creation of suspicious service files within the systemd directories on Linux platforms. It leverages logs containing file name, file path, and process GUID data from endpoints. This activity is significant for a SOC as it may indicate an adversary attempting to establish persistence on a compromised host. If confirmed malicious, this could lead to system compromise or data exfiltration, allowing attackers to maintain control over the system and execute further malicious activities.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2024-05-27
  • Author: Teoderick Contreras, Splunk
  • ID: c7495048-61b6-11ec-9a37-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1053.006 Systemd Timers Execution, Persistence, Privilege Escalation
T1053 Scheduled Task/Job Execution, Persistence, Privilege Escalation
Kill Chain Phase
  • Installation
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_name = *.service Filesystem.file_path IN ("*/etc/systemd/system*", "*/lib/systemd/system*", "*/usr/lib/systemd/system*", "*/run/systemd/system*", "*~/.config/systemd/*", "*~/.local/share/systemd/*","*/etc/systemd/user*", "*/lib/systemd/user*", "*/usr/lib/systemd/user*", "*/run/systemd/user*") by Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.process_guid Filesystem.file_path 
| `drop_dm_object_name(Filesystem)` 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)` 
| `linux_service_file_created_in_systemd_directory_filter`

Macros

The SPL above uses the following Macros:

:information_source: linux_service_file_created_in_systemd_directory_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Filesystem.dest
  • Filesystem.file_create_time
  • Filesystem.file_name
  • Filesystem.process_guid
  • Filesystem.file_path

How To Implement

To successfully implement this search, you need to be ingesting logs with the file name, file path, and process_guid executions from your endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from Splunkbase.

Known False Positives

False positives may arise when administrators or network operators create files in systemd directories for legitimate automation tasks. Therefore, it's important to adjust filter macros to account for valid activities. To implement this search successfully, it's crucial to ingest appropriate logs, preferably using the Linux Sysmon Add-on from Splunkbase for those using Sysmon.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
64.0 80 80 A service file named as $file_path$ is created in systemd folder on $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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

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