Linux auditd: Detect chattr -i removing immutable file attribute

Flags Linux processes using chattr to remove the immutable (-i) file attribute via auditd execve telemetry.

FreeReviewedSigma · Medium · v3

Product: linux
Service: auditd
Author: Jakob Weinzettl, oscd.community (SigmaHQ), DRL 1.1
Published: 2019-09-23
Updated: 2026-07-31

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1222.002Linux and Mac Permissions
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule matches executions of chattr that include the -i option, which removes the immutable file attribute. Attackers use this to modify or replace files that were protected to resist tampering, which can enable defense impairment or persistence workflows. It relies on auditd EXECVE telemetry capturing command-line arguments containing both 'chattr' and '-i'.

Reporting behind it

Related detections9 linkedT1222.002 — drag to rearrange

Suspicious File Immutability Set via chattr to Resist Removal

Suspicious File Immutability via chattr

Suspicious Making a File Executable in a Temp Directory (via process_creation)

Suspicious File Immutability Manipulation via chattr

Suspicious Download to tmp Followed by chmod Execution on Linux

Malicious Immutable Flag on SSH authorized_keys via chattr

Linux: chattr Used to Remove Immutable File Attribute

Linux chmod Process Commandlines Targeting Sensitive Directory Paths

Linux auditd: chmod/chown process execution indicating file or folder permission changes

Linux auditd: Detect chattr -i removing immutable file attribute

Pivot detection · T1222.002 · 9 related

Changelog

v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

linux-auditd-detect-chattr-removing-the-immutable-i-attribute-a5b977d6

title: "Linux auditd: Detect chattr -i removing immutable file attribute"
id: 5678d1bf-bb79-4d7f-ac0f-9b0c93681d1f
status: test
description: This rule matches executions of chattr that include the -i option, which removes the immutable file attribute. Attackers use this to modify or replace files that were protected to resist tampering, which can enable defense impairment or persistence workflows. It relies on auditd EXECVE telemetry capturing command-line arguments containing both 'chattr' and '-i'.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1222.002/T1222.002.md
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/auditd/execve/lnx_auditd_chattr_immutable_removal.yml
author: Jakob Weinzettl, oscd.community, Huntrule Team
date: 2019-09-23
modified: 2022-11-26
tags:
  - attack.defense-impairment
  - attack.t1222.002
logsource:
  product: linux
  service: auditd
detection:
  selection:
    type: EXECVE
    a0|contains: chattr
    a1|contains: -i
  condition: selection
falsepositives:
  - Administrator interacting with immutable files (e.g. for instance backups).
level: medium
simulation:
  - type: atomic-red-team
    name: Remove immutable file attribute
    technique: T1222.002
    atomic_guid: e7469fe2-ad41-4382-8965-99b94dd3c13f
license: DRL-1.1
related:
  - id: a5b977d6-8a81-4475-91b9-49dbfcd941f7
    type: derived

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