Windows WebDAV Downloader Activity via Proxy User-Agent and HTTP GET

Alerts on proxy HTTP GET requests using the Microsoft-WebDAV-MiniRedir/ User-Agent prefix associated with file download behavior.

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windows-webdav-downloader-activity-via-proxy-user-agent-and-http-get-e09aed7a

title: Windows WebDAV Downloader Activity via Proxy User-Agent and HTTP GET
id: 9bc33e11-50ed-46de-8a3d-d1e61af1f092
status: test
description: This rule flags proxy traffic where the HTTP method is GET and the User-Agent starts with Microsoft-WebDAV-MiniRedir/, which is commonly used for WebDAV-based file retrieval. Attackers may leverage WebDAV redirect/miniredir behavior to stage or download payloads as part of command-and-control. It relies on proxy telemetry capturing the HTTP request method and User-Agent string.
references:
  - https://mgreen27.github.io/posts/2018/04/02/DownloadCradle.html
  - https://github.com/SigmaHQ/sigma/blob/master/rules/web/proxy_generic/proxy_downloadcradle_webdav.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2018-04-06
modified: 2021-11-27
tags:
  - attack.command-and-control
  - attack.t1071.001
logsource:
  category: proxy
detection:
  selection:
    c-useragent|startswith: Microsoft-WebDAV-MiniRedir/
    cs-method: GET
  condition: selection
falsepositives:
  - Administrative scripts that download files from the Internet
  - Administrative scripts that retrieve certain website contents
  - Legitimate WebDAV administration
level: high
license: DRL-1.1
related:
  - id: e09aed7a-09e0-4c9a-90dd-f0d52507347e
    type: derived

What it detects

This rule flags proxy traffic where the HTTP method is GET and the User-Agent starts with Microsoft-WebDAV-MiniRedir/, which is commonly used for WebDAV-based file retrieval. Attackers may leverage WebDAV redirect/miniredir behavior to stage or download payloads as part of command-and-control. It relies on proxy telemetry capturing the HTTP request method and User-Agent string.

Known false positives

Administrative scripts that download files from the Internet
Administrative scripts that retrieve certain website contents
Legitimate WebDAV administration

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.