Suspicious PowerShell Download - PoshModule — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: test; severity: medium. Source dates: 2017-03-05 / 2023-01-20.

{
  "product": "windows",
  "category": "ps_module",
  "definition": "0ad03ef1-f21b-4a79-8ce8-e6900c54b65b"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 5da5813a240e8ab0b80b0c69988f0de1642aa2459b2ba5dd7ae2be5a0b4bdb60

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: Suspicious PowerShell Download - PoshModule
id: de41232e-12e8-49fa-86bc-c05c7e722df9
related:
    - id: 65531a81-a694-4e31-ae04-f8ba5bc33759
      type: derived
status: test
description: Detects suspicious PowerShell download command
references:
    - https://learn.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadfile?view=net-8.0
    - https://learn.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadstring?view=net-8.0
author: Florian Roth (Nextron Systems)
date: 2017-03-05
modified: 2023-01-20
tags:
    - attack.execution
    - attack.t1059.001
logsource:
    product: windows
    category: ps_module
    definition: 0ad03ef1-f21b-4a79-8ce8-e6900c54b65b
detection:
    selection_webclient_:
        ContextInfo|contains: 'System.Net.WebClient'
    selection_function:
        ContextInfo|contains:
            - '.DownloadFile('
            - '.DownloadString('
    condition: all of selection_*
falsepositives:
    - PowerShell scripts that download content from the Internet
level: medium

Original YAML and metadata in JSON

False positives

• PowerShell scripts that download content from the Internet

Source references

• https://learn.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadfile?view=net-8.0
• https://learn.microsoft.com/en-us/dotnet/api/system.net.webclient.downloadstring?view=net-8.0