Powershell Add Name Resolution Policy Table Rule

Status: test
Severity: high
Log source: category ps_script, product windows
Author: Borna Talebi
Source: github.com/SigmaHQ/sigma

Detects powershell scripts that adds a Name Resolution Policy Table (NRPT) rule for the specified namespace. This will bypass the default DNS server and uses a specified server for answering the query.

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1565` Data Manipulation

Telemetry coverage

Provider	Record / event type
PowerShell	Event ID 4104: Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body

title: Powershell Add Name Resolution Policy Table Rule
id: 4368354e-1797-463c-bc39-a309effbe8d7
status: test
description: |
  Detects powershell scripts that adds a Name Resolution Policy Table (NRPT) rule for the specified namespace.
  This will bypass the default DNS server and uses a specified server for answering the query.
references:
    - https://twitter.com/NathanMcNulty/status/1569497348841287681
    - https://learn.microsoft.com/en-us/powershell/module/dnsclient/add-dnsclientnrptrule?view=windowsserver2022-ps
author: Borna Talebi
date: 2021-09-14
modified: 2022-10-09
tags:
    - attack.impact
    - attack.t1565
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains|all:
            - 'Add-DnsClientNrptRule'
            - '-Namesp'
            - '-NameSe'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    ScriptBlockText|contains|all:
        - 'Add-DnsClientNrptRule'
        - '-Namesp'
        - '-NameSe'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ScriptBlockText`	match	`-NameSe` `-Namesp` `Add-DnsClientNrptRule`	`field:"ScriptBlockText" kind:match`