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NTLMv1 Logon Between Client and Server — Sigma Rule

Sigma rule e9d4ab66-a532-4ef7-a502-66a9e4a34f5d. NTLMv1 Logon Between Client and Server — Sigma 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.

Rule metadata and linked tags

testmediumwindowssystemattack.lateral-movementattack.t1550.002

Author: Tim Shelton, Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-04-26 / 2023-06-06.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 5afaf70983ef0d4db770d98661be56a13c8a4e7c7d12ff96f98858de5ebda90f

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: NTLMv1 Logon Between Client and Server
id: e9d4ab66-a532-4ef7-a502-66a9e4a34f5d
status: test
description: 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://github.com/nasbench/EVTX-ETW-Resources/blob/f1b010ce0ee1b71e3024180de1a3e67f99701fe4/ETWProvidersManifests/Windows10/22H2/W10_22H2_Pro_20230321_19045.2728/WEPExplorer/LsaSrv.xml
author: Tim Shelton, Nasreddine Bencherchali (Nextron Systems)
date: 2022-04-26
modified: 2023-06-06
tags:
    - attack.lateral-movement
    - attack.t1550.002
logsource:
    product: windows
    service: system
detection:
    selection:
        Provider_Name: "LsaSrv"
        EventID:
            - 6038
            - 6039
    condition: selection
falsepositives:
    - Environments that use NTLMv1
level: medium

Original YAML and metadata in JSON

False positives

  • Environments that use NTLMv1

Source references

Connected ecosystem references

Exact source-tagged techniques

Telemetry review

Read the original logsource above, then inspect the linked detection workspaces for technique-level sensor context. No per-rule telemetry equivalence is inferred.

Pinned research references. No browser attack runner, live simulation result or validated detector is asserted. Source mappings and validation limits are preserved. ATT&CK / Atomic provenance · Detection provenance.