Linux OpenVPN Privilege Escalation

SPLUNK detection rule by Gowthamaraj Rajendran, Splunk · Apache-2.0

The following analytic detects the execution of OpenVPN with elevated privileges, specifically when combined with the `--dev`, `--script-security`, `--up`, and `sudo` options. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process command-line arguments and execution details. This activity is significant because it indicates a potential privilege escalation attempt, allowing a user to execute system commands as root. If confirmed malicious, this could lead to full system compromise, enabling an attacker to gain root access and execute arbitrary commands with elevated privileges.

name: Linux OpenVPN Privilege Escalation
id: d25feebe-fa1c-4754-8a1e-afb03bedc0f2
version: 13
creation_date: '2022-08-10'
modification_date: '2026-05-13'
author: Gowthamaraj Rajendran, Splunk
status: production
type: Anomaly
description: The following analytic detects the execution of OpenVPN with elevated privileges, specifically when combined with the `--dev`, `--script-security`, `--up`, and `sudo` options. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process command-line arguments and execution details. This activity is significant because it indicates a potential privilege escalation attempt, allowing a user to execute system commands as root. If confirmed malicious, this could lead to full system compromise, enabling an attacker to gain root access and execute arbitrary commands with elevated privileges.
data_source:
    - Sysmon for Linux EventID 1
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
      WHERE Processes.process="*openvpn*"
        AND
        Processes.process="*--dev*"
        AND
        Processes.process="*--script-security*"
        AND
        Processes.process="*--up*"
        AND
        Processes.process="*sudo*"
      BY Processes.action Processes.dest Processes.original_file_name
         Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
         Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
         Processes.process Processes.process_exec Processes.process_guid
         Processes.process_hash Processes.process_id Processes.process_integrity_level
         Processes.process_name Processes.process_path Processes.user
         Processes.user_id Processes.vendor_product
    | `drop_dm_object_name(Processes)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `linux_openvpn_privilege_escalation_filter`
how_to_implement: The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
known_false_positives: False positives may be present, filter as needed.
references:
    - https://gtfobins.github.io/gtfobins/openvpn/
    - https://en.wikipedia.org/wiki/OpenVPN
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$
threat_objects:
    - field: parent_process_name
      type: parent_process_name
    - field: process_name
      type: process_name
analytic_story:
    - Linux Privilege Escalation
    - Linux Living Off The Land
asset_type: Endpoint
mitre_attack_id:
    - T1548.003
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1548/openvpn/sysmon_linux.log
          source: Syslog:Linux-Sysmon/Operational
          sourcetype: sysmon:linux
      test_type: unit

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