Linux: New user created with UID=0 or GID=0/10/27 indicating privileged group access

Alerts on Linux user creation events that assign privileged UID/GID values like root, wheel, or sudo.

FreeReviewedSigma · High · v3

Product: linux
Author: Pawel Mazur (SigmaHQ), DRL 1.1
Published: 2022-12-21
Updated: 2026-07-31

ATT&CK techniques

Persistence → Priv Esc

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1098Account Manipulation
- T1136.001Local Account
Priv Esc
- T1098Account Manipulation
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Linux user creation events that include identifiers consistent with privileged access, matching new-user log entries where UID=0 or GID=0, GID=10, or GID=27. Assigning root-level or sudo/wheel-equivalent group membership during account creation can enable immediate privilege escalation and persistence. It relies on Linux authentication logs capturing useradd-style messages containing "new user" plus UID/GID fields.

Reporting behind it

Related detections9 linkedT1136.001 — drag to rearrange

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Linux: New user created with UID=0 or GID=0/10/27 indicating privileged group access

Pivot detection · T1136.001 · 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-new-user-created-with-privileged-uid-gid-values-0ac15ec3

title: "Linux: New user created with UID=0 or GID=0/10/27 indicating privileged group access"
id: 8afac56c-d16a-4a3e-92dc-ab31e585c820
status: test
description: This rule flags Linux user creation events that include identifiers consistent with privileged access, matching new-user log entries where UID=0 or GID=0, GID=10, or GID=27. Assigning root-level or sudo/wheel-equivalent group membership during account creation can enable immediate privilege escalation and persistence. It relies on Linux authentication logs capturing useradd-style messages containing "new user" plus UID/GID fields.
references:
  - https://digital.nhs.uk/cyber-alerts/2018/cc-2825
  - https://linux.die.net/man/8/useradd
  - https://github.com/redcanaryco/atomic-red-team/blob/25acadc0b43a07125a8a5b599b28bbc1a91ffb06/atomics/T1136.001/T1136.001.md#atomic-test-5---create-a-new-user-in-linux-with-root-uid-and-gid
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/builtin/lnx_privileged_user_creation.yml
author: Pawel Mazur, Huntrule Team
date: 2022-12-21
modified: 2025-01-21
tags:
  - attack.privilege-escalation
  - attack.persistence
  - attack.t1136.001
  - attack.t1098
logsource:
  product: linux
  definition: /var/log/secure on REHL systems or /var/log/auth.log on debian like Systems needs to be collected in order for this detection to work
detection:
  selection_new_user:
    - new user
  selection_uids_gids:
    - GID=0,
    - UID=0,
    - GID=10,
    - GID=27,
  condition: all of selection_*
falsepositives:
  - Administrative activity
level: high
license: DRL-1.1
related:
  - id: 0ac15ec3-d24f-4246-aa2a-3077bb1cf90e
    type: derived

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