External Remote SMB Logon from Public IP — Sigma Rule

Rule metadata and linked tags

Author: Micah Babinski (@micahbabinski), Zach Mathis (@yamatosecurity). Source status: test; severity: high. Source dates: 2023-01-19 / 2024-03-11.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 3cfdd25fc8490d0eb062a7782b653102c44e201e35d50b6cdb85f55847db9d59

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: External Remote SMB Logon from Public IP
id: 78d5cab4-557e-454f-9fb9-a222bd0d5edc
related:
    - id: 259a9cdf-c4dd-4fa2-b243-2269e5ab18a2
      type: derived
status: test
description: Detects successful logon from public IP address via SMB. This can indicate a publicly-exposed SMB port.
references:
    - https://www.inversecos.com/2020/04/successful-4624-anonymous-logons-to.html
    - https://twitter.com/Purp1eW0lf/status/1616144561965002752
author: Micah Babinski (@micahbabinski), Zach Mathis (@yamatosecurity)
date: 2023-01-19
modified: 2024-03-11
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.initial-access
    - attack.credential-access
    - attack.stealth
    - attack.t1133
    - attack.t1078
    - attack.t1110
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4624
        LogonType: 3
    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
    filter_main_empty:
        IpAddress: '-'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Legitimate or intentional inbound connections from public IP addresses on the SMB port.
level: high

Original YAML and metadata in JSON

False positives

• Legitimate or intentional inbound connections from public IP addresses on the SMB port.

Source references

• https://www.inversecos.com/2020/04/successful-4624-anonymous-logons-to.html
• https://twitter.com/Purp1eW0lf/status/1616144561965002752