Linux Auditd Doas Tool Execution

name: Linux Auditd Doas Tool Execution
id: 91b8ca78-f205-4826-a3ef-cd8d6b24e97b
version: 10
creation_date: '2024-08-09'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: The following analytic detects the execution of the 'doas' tool on a Linux host. This tool allows standard users to perform tasks with root privileges, similar to 'sudo'. The detection leverages data from Linux Auditd, focusing on process names and command-line executions. This activity is significant as 'doas' can be exploited by adversaries to gain elevated privileges on a compromised host. If confirmed malicious, this could lead to unauthorized administrative access, potentially compromising the entire system.
data_source:
    - Linux Auditd Syscall
search: |-
    `linux_auditd` type=SYSCALL comm=doas
      | rename host as dest
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY comm exe syscall
           uid ppid pid
           success dest
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `linux_auditd_doas_tool_execution_filter`
how_to_implement: To implement this detection, the process begins by ingesting auditd data, that consist SYSCALL, TYPE, EXECVE and PROCTITLE events, which captures command-line executions and process details on Unix/Linux systems. These logs should be ingested and processed using Splunk Add-on for Unix and Linux (https://splunkbase.splunk.com/app/833), which is essential for correctly parsing and categorizing the data. The next step involves normalizing the field names  to match the field names set by the Splunk Common Information Model (CIM) to ensure consistency across different data sources and enhance the efficiency of data modeling. This approach enables effective monitoring and detection of linux endpoints where auditd is deployed
known_false_positives: Administrator or network operator can execute this command. Please update the filter macros to remove false positives.
references:
    - https://wiki.gentoo.org/wiki/Doas
    - https://www.makeuseof.com/how-to-install-and-use-doas/
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: A SYSCALL - [$comm$] event was executed on host - [$dest$] to execute the "doas" tool.
analytic_story:
    - Linux Privilege Escalation
    - Linux Persistence Techniques
    - Compromised Linux Host
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/T1548.003/linux_auditd_doas_new/linux_auditd_new_doas.log
          source: auditd
          sourcetype: auditd
      test_type: unit