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Detection rules › Sigma

DNS TXT Answer with Possible Execution Strings

Status
test
Severity
high
Log source
category dns
Author
Markus Neis
Source
github.com/SigmaHQ/sigma

Detects strings used in command execution in DNS TXT Answer

MITRE ATT&CK coverage

TacticTechniques
Command & ControlT1071.004 Application Layer Protocol: DNS

Rule body yaml

title: DNS TXT Answer with Possible Execution Strings
id: 8ae51330-899c-4641-8125-e39f2e07da72
status: test
description: Detects strings used in command execution in DNS TXT Answer
references:
    - https://twitter.com/stvemillertime/status/1024707932447854592
    - https://github.com/samratashok/nishang/blob/414ee1104526d7057f9adaeee196d91ae447283e/Backdoors/DNS_TXT_Pwnage.ps1
author: Markus Neis
date: 2018-08-08
modified: 2021-11-27
tags:
    - attack.command-and-control
    - attack.t1071.004
logsource:
    category: dns
detection:
    selection:
        record_type: 'TXT'
        answer|contains:
            - 'IEX'
            - 'Invoke-Expression'
            - 'cmd.exe'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    record_type: 'TXT'
    answer|contains:
        - 'IEX'
        - 'Invoke-Expression'
        - 'cmd.exe'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
answermatch
  • IEX
  • Invoke-Expression
  • cmd.exe
record_typeeq
  • TXT