Suspicious NTLMv1 Logon Between Client and Server (via system)

title: Suspicious NTLMv1 Logon Between Client and Server (via system)
id: fc242f0a-0159-5f25-b43f-ba80ff0de615
status: stable
description: This rule detects the reporting of NTLMv1 being used between a client and server. NTLMv1 is insecure as the underlying encryption algorithms can be brute-forced by modern hardware.
references:
    - https://attack.mitre.org/techniques/T1550/002/
    - https://github.com/nasbench/EVTX-ETW-Resources/blob/f1b010ce0ee1b71e3024180de1a3e67f99701fe4/ETWProvidersManifests/Windows10/22H2/W10_22H2_Pro_20230321_19045.2728/WEPExplorer/LsaSrv.xml
author: Huntrule Team
date: 2026-03-26
tags:
    - attack.lateral-movement
    - attack.t1550.002
logsource:
    product: windows
    service: system
detection:
    selection:
        Provider_Name: "LsaSrv"
        EventID:
            - 6038
            - 6039
    condition: selection
falsepositives:
    - Unknown
level: medium