title: Failed Logon From Public IP
id: f88e112a-21aa-44bd-9b01-6ee2a2bbbed1
description: A login from a public IP can indicate a misconfigured firewall or network boundary.
author: NVISO
date: 2020/05/06
tags:
    - attack.initial_access
    - attack.persistence
    - attack.t1078
    - attack.t1190
    - attack.t1133
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4625
    unknown:
        IpAddress|contains: '-'
    privatev4:
        IpAddress|startswith:
            - '10.' #10.0.0.0/8
            - '192.168.' #192.168.0.0/16
            - '172.16.' #172.16.0.0/12
            - '172.17.'
            - '172.18.'
            - '172.19.'
            - '172.20.'
            - '172.21.'
            - '172.22.'
            - '172.23.'
            - '172.24.'
            - '172.25.'
            - '172.26.'
            - '172.27.'
            - '172.28.'
            - '172.29.'
            - '172.30.'
            - '172.31.'
            - '127.' #127.0.0.0/8
            - '169.254.' #169.254.0.0/16
    privatev6:
        - IpAddress: '::1' #loopback 
        - IpAddress|startswith:
            - 'fe80::' #link-local
            - 'fc00::' #unique local
    condition: selection and not (unknown or privatev4 or privatev6)
falsepositives:
    - Legitimate logon attempts over the internet
    - IPv4-to-IPv6 mapped IPs
level: medium