Linux Auditd Setuid Using Chmod Utility

SPLUNK detection rule by Teoderick Contreras, Splunk · Apache-2.0

The following analytic detects the execution of the chmod utility to set the SUID or SGID bit on files, which can allow users to temporarily gain root or group-level access. This detection leverages data from Linux Auditd, focusing on process names and command-line arguments related to chmod. This activity is significant as it can indicate an attempt to escalate privileges or maintain persistence on a system. If confirmed malicious, an attacker could gain elevated access, potentially compromising sensitive data or critical system functions.

name: Linux Auditd Setuid Using Chmod Utility
id: 8230c407-1b47-4d95-ac2e-718bd6381386
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 chmod utility to set the SUID or SGID bit on files, which can allow users to temporarily gain root or group-level access. This detection leverages data from Linux Auditd, focusing on process names and command-line arguments related to chmod. This activity is significant as it can indicate an attempt to escalate privileges or maintain persistence on a system. If confirmed malicious, an attacker could gain elevated access, potentially compromising sensitive data or critical system functions.
data_source:
    - Linux Auditd Proctitle
search: |-
    `linux_auditd`  proctitle IN ("*chmod *")  AND proctitle IN ("* u+s *", "* g+s *", "* 4777 *", "* 4577 *")
      | rename host as dest
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY proctitle dest
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `linux_auditd_setuid_using_chmod_utility_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://www.hackingarticles.in/linux-privilege-escalation-using-capabilities/
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 [$proctitle$] event occurred on host - [$dest$] to set the SUID or SGID bit on files using the chmod utility.
analytic_story:
    - Linux Living Off The Land
    - Linux Privilege Escalation
    - Linux Persistence Techniques
    - Compromised Linux Host
asset_type: Endpoint
mitre_attack_id:
    - T1548.001
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/T1548.001/linux_auditd_setuid/auditd_proctitle_setuid.log
          source: auditd
          sourcetype: auditd
      test_type: unit

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c5942c31-139e-44be-93a9-42d48aab486c

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Executable code, not a declarative rule

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