name: Linux OpenVPN Privilege Escalation
id: d25feebe-fa1c-4754-8a1e-afb03bedc0f2
version: 1
date: '2022-08-11'
author: Gowthamaraj Rajendran, Splunk
status: production
type: Anomaly
description: OpenVPN is a virtual private network system that implements techniques
  to create secure point-to-point or site-to-site connections in routed or bridged
  configurations and remote access facilities. It implements both client and server
  applications. If sudo right is given to the OpenVPN application for the user, then
  the user can run system commands as root and possibly get a root shell.
data_source:
- Sysmon Event ID 1
search:
  selection1:
    CommandLine: '*--dev*'
  selection2:
    CommandLine: '*openvpn*'
  selection3:
    CommandLine: '*--script-security*'
  selection4:
    CommandLine: '*--up*'
  selection5:
    CommandLine: '*sudo*'
  condition: selection1 and selection2 and selection3 and selection4 and selection5
how_to_implement: To successfully implement this search, you need to be ingesting
  logs with the process name, parent process, and command-line executions from your
  endpoints into the Endpoint datamodel. If you are using Sysmon, you can use the
  Add-on for Linux Sysmon from Splunkbase.
known_false_positives: False positives may be present, filter as needed.
references:
- https://gtfobins.github.io/gtfobins/openvpn/
- https://en.wikipedia.org/wiki/OpenVPN
tags:
  analytic_story:
  - Linux Privilege Escalation
  - Linux Living Off The Land
  asset_type: Endpoint
  confidence: 50
  impact: 60
  message: An instance of $parent_process_name$ spawning $process_name$ was identified
    on endpoint $dest$
  mitre_attack_id:
  - T1548.003
  - T1548
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  - name: parent_process_name
    type: Process
    role:
    - Parent Process
  - name: process_name
    type: Process
    role:
    - Child Process
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  risk_score: 30
  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
    update_timestamp: true