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« Kernel Load or Unload via Kexec Detected Kernel Module Removal »

Kernel Module Load via insmodedit

Detects the use of the insmod binary to load a Linux kernel object file. Threat actors can use this binary, given they have root privileges, to load a rootkit on a system providing them with complete control and the ability to hide from security products. Manually loading a kernel module in this manner should not be at all common and can indicate suspcious or malicious behavior.

Rule type: eql

Rule indices:

  • logs-endpoint.events.*
  • endgame-*
  • auditbeat-*
  • logs-auditd_manager.auditd-*

Severity: medium

Risk score: 47

Runs every: 5m

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

Maximum alerts per execution: 100

References:

Tags:

  • Domain: Endpoint
  • OS: Linux
  • Use Case: Threat Detection
  • Tactic: Persistence
  • Threat: Rootkit
  • Data Source: Elastic Endgame
  • Data Source: Elastic Defend
  • Data Source: Auditd Manager

Version: 109

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guideedit

Triage and analysis

Investigating Kernel module load via insmod

The insmod binary is a Linux utility that allows users with root privileges to load kernel modules, which are object files that extend the functionality of the kernel.

Threat actors can abuse this utility to load rootkits, granting them full control over the system and the ability to evade security products.

The detection rule Kernel module load via insmod is designed to identify instances where the insmod binary is used to load a kernel object file (with a .ko extension) on a Linux system. This activity is uncommon and may indicate suspicious or malicious behavior.

Note: This investigation guide uses the Osquery Markdown Plugin introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide. This investigation guide uses placeholder fields to dynamically pass alert data into Osquery queries. Placeholder fields were introduced in Elastic Stack version 8.7.0. If you’re using Elastic Stack version 8.6.0 or earlier, you’ll need to manually adjust this investigation guide’s queries to ensure they properly run.

Possible investigation steps

  • Investigate the kernel object file that was loaded via insmod.
  • !{osquery{"label":"Osquery - Retrieve Running Processes by User","query":"SELECT pid, username, name FROM processes p JOIN users u ON u.uid = p.uid ORDER BY username"}}
  • Investigate the script execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence and whether they are located in expected locations.
  • !{osquery{"label":"Osquery - Retrieve Listening Ports","query":"SELECT pid, address, port, socket, protocol, path FROM listening_ports"}}
  • Investigate the kernel ring buffer for any warnings or messages, such as tainted or out-of-tree kernel module loads through dmesg.
  • Investigate syslog for any unusual segfaults or other messages. Rootkits may be installed on targets with different architecture as expected, and could potentially cause segmentation faults.
  • Investigate other alerts associated with the user/host during the past 48 hours.
  • Validate the activity is not related to planned patches, updates, network administrator activity, or legitimate software installations.
  • Investigate whether the altered scripts call other malicious scripts elsewhere on the file system.
  • If scripts or executables were dropped, retrieve the files and determine if they are malicious:
  • Use a private sandboxed malware analysis system to perform analysis.
  • Observe and collect information about the following activities:
  • Attempts to contact external domains and addresses.
  • Check if the domain is newly registered or unexpected.
  • Check the reputation of the domain or IP address.
  • File access, modification, and creation activities.
  • Investigate abnormal behaviors by the subject process/user such as network connections, file modifications, and any other spawned child processes.
  • Investigate listening ports and open sockets to look for potential command and control traffic or data exfiltration.
  • !{osquery{"label":"Osquery - Retrieve Open Sockets","query":"SELECT pid, family, remote_address, remote_port, socket, state FROM process_open_sockets"}}
  • !{osquery{"label":"Osquery - Retrieve Information for a Specific User","query":"SELECT * FROM users WHERE username = {{user.name}}"}}
  • Identify the user account that performed the action, analyze it, and check whether it should perform this kind of action.
  • !{osquery{"label":"Osquery - Investigate the Account Authentication Status","query":"SELECT * FROM logged_in_users WHERE user = {{user.name}}"}}
  • Investigate whether the user is currently logged in and active.
  • $osquery_6

False positive analysis

  • If this activity is related to new benign software installation activity, consider adding exceptions — preferably with a combination of user and command line conditions.
  • If this activity is related to a system administrator who uses cron jobs for administrative purposes, consider adding exceptions for this specific administrator user account.
  • Try to understand the context of the execution by thinking about the user, machine, or business purpose. A small number of endpoints, such as servers with unique software, might appear unusual but satisfy a specific business need.

Related Rules

  • Kernel Driver Load - 3e12a439-d002-4944-bc42-171c0dcb9b96
  • Tainted Out-Of-Tree Kernel Module Load - 51a09737-80f7-4551-a3be-dac8ef5d181a
  • Tainted Kernel Module Load - 05cad2fb-200c-407f-b472-02ea8c9e5e4a
  • Attempt to Clear Kernel Ring Buffer - 2724808c-ba5d-48b2-86d2-0002103df753
  • Enumeration of Kernel Modules via Proc - 80084fa9-8677-4453-8680-b891d3c0c778
  • Suspicious Modprobe File Event - 40ddbcc8-6561-44d9-afc8-eefdbfe0cccd
  • Kernel Module Removal - cd66a5af-e34b-4bb0-8931-57d0a043f2ef
  • Enumeration of Kernel Modules - 2d8043ed-5bda-4caf-801c-c1feb7410504

Response and Remediation

  • Initiate the incident response process based on the outcome of the triage.
  • Isolate the involved host to prevent further post-compromise behavior.
  • If the triage identified malware, search the environment for additional compromised hosts.
  • Implement temporary network rules, procedures, and segmentation to contain the malware.
  • Stop suspicious processes.
  • Immediately block the identified indicators of compromise (IoCs).
  • Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
  • Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
  • Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
  • Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  • Leverage the incident response data and logging to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).

Setupedit

Setup

This rule requires data coming in from Elastic Defend.

Elastic Defend Integration Setup

Elastic Defend is integrated into the Elastic Agent using Fleet. Upon configuration, the integration allows the Elastic Agent to monitor events on your host and send data to the Elastic Security app.

Prerequisite Requirements:

  • Fleet is required for Elastic Defend.
  • To configure Fleet Server refer to the documentation.

The following steps should be executed in order to add the Elastic Defend integration on a Linux System:

  • Go to the Kibana home page and click "Add integrations".
  • In the query bar, search for "Elastic Defend" and select the integration to see more details about it.
  • Click "Add Elastic Defend".
  • Configure the integration name and optionally add a description.
  • Select the type of environment you want to protect, either "Traditional Endpoints" or "Cloud Workloads".
  • Select a configuration preset. Each preset comes with different default settings for Elastic Agent, you can further customize these later by configuring the Elastic Defend integration policy. Helper guide.
  • We suggest selecting "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
  • Enter a name for the agent policy in "New agent policy name". If other agent policies already exist, you can click the "Existing hosts" tab and select an existing policy instead. For more details on Elastic Agent configuration settings, refer to the helper guide.
  • Click "Save and Continue".
  • To complete the integration, select "Add Elastic Agent to your hosts" and continue to the next section to install the Elastic Agent on your hosts. For more details on Elastic Defend refer to the helper guide.

Rule queryedit

process where host.os.type == "linux" and event.type == "start" and process.name == "insmod" and process.args : "*.ko"

Framework: MITRE ATT&CKTM

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