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Detection rules › Sigma

FortiGate - New Local User Created

Status
experimental
Severity
medium
Log source
product fortigate, service event
Author
Marco Pedrinazzi (@pedrinazziM) (InTheCyber)
Source
github.com/SigmaHQ/sigma

Detects the creation of a new local user on a Fortinet FortiGate Firewall. The new local user could be used for VPN connections.

Known false positives

  • A local user can be created for legitimate purposes. Investigate the user details to determine if it is authorized.

MITRE ATT&CK coverage

TacticTechniques
Persistence

Rule body

title: FortiGate - New Local User Created
id: ddbbe845-1d74-43a8-8231-2156d180234d
status: experimental
description: |
    Detects the creation of a new local user on a Fortinet FortiGate Firewall.
    The new local user could be used for VPN connections.
references:
    - https://www.fortiguard.com/psirt/FG-IR-24-535
    - https://docs.fortinet.com/document/fortigate/7.6.4/fortios-log-message-reference/398/event
    - https://docs.fortinet.com/document/fortigate/7.6.4/cli-reference/109120963/config-user-local
    - https://docs.fortinet.com/document/fortigate/7.6.4/fortios-log-message-reference/44547/44547-logid-event-config-objattr
author: Marco Pedrinazzi (@pedrinazziM) (InTheCyber)
date: 2025-11-01
tags:
    - attack.persistence
    - attack.t1136.001
logsource:
    product: fortigate
    service: event
detection:
    selection:
        action: 'Add'
        cfgpath: 'user.local'
    condition: selection
falsepositives:
    - A local user can be created for legitimate purposes. Investigate the user details to determine if it is authorized.
level: medium

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    action: 'Add'
    cfgpath: 'user.local'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
actioneq
  • Add
field:"action" kind:eq value:"Add"
cfgpatheq
  • user.local
field:"cfgpath" kind:eq value:"user.local"