Linux: Creation or Modification of Systemd Service

Rule ID

PH_Rule_TH_EQLLIB_LINUX_18

Default Status

Enabled

Description

Systemd services can be used to establish persistence on a Linux system. The systemd service manager is commonly used for managing background daemon processes (also known as services) and other system resources.

Severity

MITRE ATT&CK® Tactics

Persistence

Persistence consists of techniques that adversaries use to keep access to systems across restarts, changed credentials, and other interruptions that could cut off their access. Techniques used for persistence include any access, action, or configuration changes that let them maintain their foothold on systems, such as replacing or hijacking legitimate code or adding startup code.

https://attack.mitre.org/tactics/TA0003

MITRE ATT&CK® Techniques

T1543.002

Create or Modify System Process: Systemd Service

Adversaries may create or modify systemd services to repeatedly execute malicious payloads as part of persistence. The systemd service manager is commonly used for managing background daemon processes (also known as services) and other system resources. Adversaries have used systemd functionality to establish persistent access to victim systems by creating and/or modifying service unit files that cause systemd to execute malicious commands at recurring intervals, such as at system boot.

https://attack.mitre.org/techniques/T1543/002

Impacts

Server

Data Source

Linux File Monitoring via FortiSIEM Agent

Detection

Correlation

Remediation Guidance

No remediation guidance specified

Time Window

If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.

300 seconds

Trigger Conditions

If the following defined pattern/s occur within a 300 second time window.

Filter

SubPattern Definitions

SubPattern Name: Filter

This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.

SubPattern Query

This is the query logic that matches incoming events

eventType != "FSM_LINUX_FILE_DELETE" AND targetOsObjName CONTAIN ".service" AND targetOsObjName REGEXP ("/etc/systemd/system/.*|/usr/lib/systemd/system/.*")

Group by Attributes

This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID

hostName,targetOsObjName

Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 1

Incident Attribute Mapping

This section defines which fields in matching raw events should be mapped to the incident attributes in the resulting incident.

The available raw event attributes to map are limited to the group by attributes and the aggregate event constraint fields for each subpattern

 hostName = Filter.hostName,
targetOsObjName = Filter.targetOsObjName

FortiSIEM Rules