splunk_escuAnomaly

Linux Auditd File Permission Modification Via Chmod

The following analytic detects suspicious file permission modifications using the `chmod` command, which may indicate an attacker attempting to alter access controls on critical files or directories. Such modifications can be used to grant unauthorized users elevated privileges or to conceal malicious activities by restricting legitimate access. By monitoring for unusual or unauthorized `chmod` usage, this analytic helps identify potential security breaches, allowing security teams to respond promptly to prevent privilege escalation, data tampering, or other unauthorized actions on the system.

MITRE ATT&CK

T1222.002

Detection Query

`linux_auditd` proctitle="*chmod*" AND proctitle IN ("* 777 *", "* 755 *", "*+*x*", "* 754 *")
  | 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_file_permission_modification_via_chmod_filter`

Author

Teoderick Contreras, Splunk, Ivar Nygård

Created

2026-03-31

Data Sources

Linux Auditd Proctitle

References

https://www.splunk.com/en_us/blog/security/deep-dive-on-persistence-privilege-escalation-technique-and-detection-in-linux-platform.html

Tags

Linux Persistence TechniquesCompromised Linux HostChina-Nexus Threat ActivityLinux Living Off The LandXorDDosSalt TyphoonLinux Privilege EscalationAxios Supply Chain Post Compromise

Raw Content

name: Linux Auditd File Permission Modification Via Chmod
id: 5f1d2ea7-eec0-4790-8b24-6875312ad492
version: 14
date: '2026-03-31'
author: "Teoderick Contreras, Splunk, Ivar Nygård"
status: production
type: Anomaly
description: The following analytic detects suspicious file permission modifications using the `chmod` command, which may indicate an attacker attempting to alter access controls on critical files or directories. Such modifications can be used to grant unauthorized users elevated privileges or to conceal malicious activities by restricting legitimate access. By monitoring for unusual or unauthorized `chmod` usage, this analytic helps identify potential security breaches, allowing security teams to respond promptly to prevent privilege escalation, data tampering, or other unauthorized actions on the system.
data_source:
    - Linux Auditd Proctitle
search: |-
    `linux_auditd` proctitle="*chmod*" AND proctitle IN ("* 777 *", "* 755 *", "*+*x*", "* 754 *")
      | 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_file_permission_modification_via_chmod_filter`
how_to_implement: To implement this detection, the process begins by ingesting auditd data, that consists of 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 use this application for automation purposes. Please update the filter macros to remove false positives.
references:
    - https://www.splunk.com/en_us/blog/security/deep-dive-on-persistence-privilege-escalation-technique-and-detection-in-linux-platform.html
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 ("$dest$") starthoursago=168  | 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: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: A $proctitle$ event occurred on host $dest$ to modify file permissions using the "chmod" command.
    risk_objects:
        - field: dest
          type: system
          score: 20
    threat_objects: []
tags:
    analytic_story:
        - Linux Persistence Techniques
        - Compromised Linux Host
        - China-Nexus Threat Activity
        - Linux Living Off The Land
        - XorDDos
        - Salt Typhoon
        - Linux Privilege Escalation
        - Axios Supply Chain Post Compromise
    asset_type: Endpoint
    mitre_attack_id:
        - T1222.002
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1222.002/linux_auditd_chmod_exec_attrib/auditd_proctitle_chmod.log
          source: auditd
          sourcetype: auditd