DNS TXT Answer with Possible Execution Strings — Sigma Rule

Rule metadata and linked tags

Author: Markus Neis. Source status: test; severity: high. Source dates: 2018-08-08 / 2021-11-27.

{
  "category": "dns"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 9a5e44aa6e074e7d681b52060dbe465b3ecaec828587f8c19c1a11387e91c120

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: 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

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://twitter.com/stvemillertime/status/1024707932447854592
• https://github.com/samratashok/nishang/blob/414ee1104526d7057f9adaeee196d91ae447283e/Backdoors/DNS_TXT_Pwnage.ps1