Suspicious Unsigned or Unencrypted SMB Connection to Share Established (via smbserver-connectivity)

title: Suspicious Unsigned or Unencrypted SMB Connection to Share Established (via smbserver-connectivity)
id: ec247b55-1b95-567e-9c84-5611efa7fff1
status: stable
description: This rule detects SMB server connections to shares without signing or encryption enabled. This could indicate potential lateral movement behavior using unsecured SMB shares.
author: Huntrule Team
date: 2026-06-04
references:
    - https://attack.mitre.org/techniques/T1021/002/
    - https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/overview-server-message-block-signing
tags:
    - attack.lateral-movement
    - attack.t1021.002
logsource:
    product: windows
    service: smbserver-connectivity
detection:
    selection_shares:
        EventID: 4000
        ShareName|contains:
            - 'IPC$'
            - 'ADMIN$'
            - 'C$'
    selection_status:
        - SigningUsed: 'false'
        - EncyptionUsed: 'false'
    filter_main_local_ips:
        - ClientAddress|cidr:
              - '127.0.0.0/8'
              - '169.254.0.0/16'
              - '::1/128'
              - 'fe80::/10'
              - 'fc00::/7'
        - ClientAddress|contains:
              - '00000000000000000000000000000001'
              - 'FE80000000000000'
              - 'FC00000000000000'
              - '0200????7F'
              - '0200????A9FE'
    condition: all of selection_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium