This analytic looks for suspicious file creation in systemd timer directory in linux platform. systemd is a system and service manager for Linux distributions. From the Windows perspective, this process fulfills the duties of wininit.exe and services.exe combined. At the risk of simplifying the functionality of systemd, it initializes a Linux system and starts relevant services that are defined in service unit files. Adversaries, malware and red teamers may abuse this this feature by stashing systemd service file to persist on the targetted or compromised host.
- Type: Anomaly
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2021-12-20
- Author: Teoderick Contreras, Splunk
- ID: c7495048-61b6-11ec-9a37-acde48001122
Kill Chain Phase
- CIS 3
- CIS 5
- CIS 16
1 2 3 4 5 6 | 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`
The SPL above uses the following Macros:
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.
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
Administrator or network operator can create file in systemd folders for automation purposes. Please update the filter macros to remove false positives.
Associated Analytic story
|64.0||80||80||A service file named as $file_path$ is created in systemd folder on $dest$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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