NTLM Brute Force

Status: test
Severity: medium
Log source: product windows, service ntlm
Author: Jerry Shockley '@jsh0x'
Source: github.com/SigmaHQ/sigma

Detects common NTLM brute force device names

Known false positives

Systems with names equal to the spoofed ones used by the brute force tools

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1110` Brute Force

Telemetry coverage

Provider	Record / event type
NTLM	Event ID 8004: NTLM authentication in this domain audit (domain controller): Audit NTLM authentication in this domain.

Rule body

title: NTLM Brute Force
id: 9c8acf1a-cbf9-4db6-b63c-74baabe03e59
status: test
description: Detects common NTLM brute force device names
references:
    - https://www.varonis.com/blog/investigate-ntlm-brute-force
author: Jerry Shockley '@jsh0x'
date: 2022-02-02
tags:
    - attack.credential-access
    - attack.t1110
logsource:
    product: windows
    service: ntlm
    definition: Requires events from Microsoft-Windows-NTLM/Operational
detection:
    selection:
        EventID: 8004
    devicename:
        WorkstationName:
            - 'Rdesktop'
            - 'Remmina'
            - 'Freerdp'
            - 'Windows7'
            - 'Windows8'
            - 'Windows2012'
            - 'Windows2016'
            - 'Windows2019'
    condition: selection and devicename
falsepositives:
    - Systems with names equal to the spoofed ones used by the brute force tools
level: medium

Stages and Predicates

Stage 0: `condition`

selection and devicename

Stage 1: `selection`

selection:
    EventID: 8004

Stage 2: `devicename`

devicename:
    WorkstationName:
        - 'Rdesktop'
        - 'Remmina'
        - 'Freerdp'
        - 'Windows7'
        - 'Windows8'
        - 'Windows2012'
        - 'Windows2016'
        - 'Windows2019'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`WorkstationName`	eq	`Freerdp` `Rdesktop` `Remmina` `Windows2012` `Windows2016` `Windows2019` `Windows7` `Windows8`	`field:"WorkstationName" kind:eq`

NTLM Brute Force

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: devicename

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `devicename`