Detection rules › Sigma
PowerShell Download Via Net.WebClient - PowerShell Classic
Detects PowerShell download activity, via the .DownloadFile() or .DownloadString() methods of the Net.WebClient class. This technique is often abused by attackers to download additional payloads.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Execution | T1059.001 Command and Scripting Interpreter: PowerShell |
| Command & Control | T1105 Ingress Tool Transfer |
Event coverage
| Provider | Event |
|---|---|
| PowerShell | Event ID 400 |
Rule body yaml
title: PowerShell Download Via Net.WebClient - PowerShell Classic
id: 3236fcd0-b7e3-4433-b4f8-86ad61a9af2d
related:
- id: 65531a81-a694-4e31-ae04-f8ba5bc33759
type: derived
status: test
description: |
Detects PowerShell download activity, via the .DownloadFile() or .DownloadString() methods of the Net.WebClient class.
This technique is often abused by attackers to download additional payloads.
references:
- https://www.trendmicro.com/en_us/research/22/j/lv-ransomware-exploits-proxyshell-in-attack.html
author: Florian Roth (Nextron Systems)
date: 2017-03-05
modified: 2026-04-28
tags:
- attack.execution
- attack.command-and-control
- attack.t1059.001
- attack.t1105
logsource:
product: windows
category: ps_classic_start
detection:
selection_webclient:
Data|contains: 'Net.WebClient'
selection_download:
Data|contains:
- '.DownloadFile('
- '.DownloadString('
condition: all of selection_*
falsepositives:
- This activity may be used by legitimate software, such as patch management tools or software updaters. Investigate any such activity and apply the necessary filter.
level: low
Stages and Predicates
Stage 0: condition
all of selection_*Stage 1: selection_webclient
selection_webclient:
Data|contains: 'Net.WebClient'
Stage 2: selection_download
selection_download:
Data|contains:
- '.DownloadFile('
- '.DownloadString('
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.
| Field | Kind | Values |
|---|---|---|
Data | match |
|