NetNTLM Downgrade Attack

Status: test
Severity: high
Log source: product windows, service security
Author: Florian Roth (Nextron Systems), wagga
Source: github.com/SigmaHQ/sigma

Detects NetNTLM downgrade attack

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1112` Modify Registry
Defense Impairment	`T1112` Modify Registry `T1685` Disable or Modify Tools

Telemetry coverage

Provider	Record / event type
Security-Auditing	Event ID 4657: A registry value was modified.

Rule body

title: NetNTLM Downgrade Attack
id: d3abac66-f11c-4ed0-8acb-50cc29c97eed
related:
    - id: d67572a0-e2ec-45d6-b8db-c100d14b8ef2
      type: derived
status: test
description: Detects NetNTLM downgrade attack
references:
    - https://www.optiv.com/blog/post-exploitation-using-netntlm-downgrade-attacks
author: Florian Roth (Nextron Systems), wagga
date: 2018-03-20
modified: 2022-10-09
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1685
    - attack.t1112
logsource:
    product: windows
    service: security
    definition: 'Requirements: Audit Policy : Object Access > Audit Registry (Success)'
detection:
    selection:
        EventID: 4657
        ObjectName|contains|all:
            - '\REGISTRY\MACHINE\SYSTEM'
            - 'ControlSet'
            - '\Control\Lsa'
        ObjectValueName:
            - 'LmCompatibilityLevel'
            - 'NtlmMinClientSec'
            - 'RestrictSendingNTLMTraffic'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    EventID: 4657
    ObjectName|contains|all:
        - '\REGISTRY\MACHINE\SYSTEM'
        - 'ControlSet'
        - '\Control\Lsa'
    ObjectValueName:
        - 'LmCompatibilityLevel'
        - 'NtlmMinClientSec'
        - 'RestrictSendingNTLMTraffic'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ObjectName`	match	`ControlSet` `\Control\Lsa` `\REGISTRY\MACHINE\SYSTEM` corpus 2 (sigma 2)	`field:"ObjectName" kind:match`
`ObjectValueName`	eq	`LmCompatibilityLevel` `NtlmMinClientSec` `RestrictSendingNTLMTraffic`	`field:"ObjectValueName" kind:eq`

NetNTLM Downgrade Attack

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`