Failed Logon From Public IP — Sigma Rule

Rule metadata and linked tags

Author: NVISO. Source status: test; severity: medium. Source dates: 2020-05-06 / 2024-03-11.

{
  "product": "windows",
  "service": "security"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 2b340875ecf8432e60158f67cccb398068d61af24cc92ff9c341d73f2308b4f0

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: Failed Logon From Public IP
id: f88e112a-21aa-44bd-9b01-6ee2a2bbbed1
status: test
description: Detects a failed logon attempt from a public IP. A login from a public IP can indicate a misconfigured firewall or network boundary.
references:
    - https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4625
author: NVISO
date: 2020-05-06
modified: 2024-03-11
tags:
    - attack.privilege-escalation
    - attack.initial-access
    - attack.persistence
    - attack.stealth
    - attack.t1078
    - attack.t1190
    - attack.t1133
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4625
    filter_main_ip_unknown:
        IpAddress|contains: '-'
    filter_main_local_ranges:
        IpAddress|cidr:
            - '::1/128'  # IPv6 loopback
            - '10.0.0.0/8'
            - '127.0.0.0/8'
            - '172.16.0.0/12'
            - '192.168.0.0/16'
            - '169.254.0.0/16'
            - 'fc00::/7'  # IPv6 private addresses
            - 'fe80::/10'  # IPv6 link-local addresses
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Legitimate logon attempts over the internet
    - IPv4-to-IPv6 mapped IPs
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate logon attempts over the internet
• IPv4-to-IPv6 mapped IPs

Source references

• https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4625