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Suspicious Sysctl File Eventedit

Monitors file events on sysctl configuration files (e.g., /etc/sysctl.conf, /etc/sysctl.d/*.conf) to identify potential unauthorized access or manipulation of system-level configuration settings. Attackers may tamper with the sysctl configuration files to modify kernel parameters, potentially compromising system stability, performance, or security.

Rule type: eql

Rule indices:

  • auditbeat-*
  • logs-auditd_manager.auditd-*

Severity: low

Risk score: 21

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

  • OS: Linux
  • Use Case: Threat Detection
  • Tactic: Discovery

Version: 1

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guideedit

## Setup
This rule requires the use of the `auditd_manager` integration. `Auditd_manager` is a tool designed to simplify and enhance the management of the audit subsystem in Linux systems. It provides a user-friendly interface and automation capabilities for configuring and monitoring system auditing through the auditd daemon. With `auditd_manager`, administrators can easily define audit rules, track system events, and generate comprehensive audit reports, improving overall security and compliance in the system. The following steps should be executed in order to install and deploy `auditd_manager` on a Linux system.

```
Kibana -->
Management -->
Integrations -->
Auditd Manager -->
Add Auditd Manager
```

`Auditd_manager` subscribes to the kernel and receives events as they occur without any additional configuration. However, if more advanced configuration is required to detect specific behavior, audit rules can be added to the integration in either the "audit rules" configuration box or the "auditd rule files" box by specifying a file to read the audit rules from.

For this detection rule to trigger, the following additional audit rules are required to be added to the integration:

```
-w /etc/sysctl.conf -p wa -k sysctl
-w /etc/sysctl.d -p wa -k sysctl
```

Add the newly installed `auditd manager` to an agent policy, and deploy the agent on a Linux system from which auditd log files are desirable.

Rule queryedit

file where host.os.type == "linux" and event.action in ("opened-file", "read-file", "wrote-to-file") and
file.path : ("/etc/sysctl.conf", "/etc/sysctl.d", "/etc/sysctl.d/*") and not process.name == "auditbeat"

Framework: MITRE ATT&CKTM

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