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FortiGate - New Local User Created — Sigma Rule

Sigma rule ddbbe845-1d74-43a8-8231-2156d180234d. FortiGate - New Local User Created — Sigma Rule. Detects the creation of a new local user on a Fortinet FortiGate Firewall. The new local user could be used for VPN connections.

Rule metadata and linked tags

experimentalmediumfortigateeventattack.persistenceattack.t1136.001

Author: Marco Pedrinazzi @pedrinazziM (InTheCyber). Source status: experimental; severity: medium. Source dates: 2025-11-01 / not supplied.

{
  "product": "fortigate",
  "service": "event"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: e4af3e66b590041d027944daa344ad50e5aff0500c9217117e4893a8e8e766b8

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

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

Original YAML and metadata in JSON

False positives

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

Source references

Connected ecosystem references

Exact source-tagged techniques

Telemetry review

Read the original logsource above, then inspect the linked detection workspaces for technique-level sensor context. No per-rule telemetry equivalence is inferred.

Pinned research references. No browser attack runner, live simulation result or validated detector is asserted. Source mappings and validation limits are preserved. ATT&CK / Atomic provenance · Detection provenance.