huntrule

Windows Browser Process File Download via Inline URL and Suspicious Extension

Flags Windows browser processes launched with an inline HTTP URL pointing to files with suspicious extensions.

FreeUnreviewedSigmamediumv1
title: Windows Browser Process File Download via Inline URL and Suspicious Extension
id: fc9ebdb2-821d-4934-ba59-09b9b5a57ee4
status: test
description: This rule identifies Windows executions of common browser processes where the command line includes an inline URL containing an HTTP scheme and ends with one of several potentially risky file extensions. Attackers can abuse browser invocation with a URL to trigger downloads of arbitrary payloads or reduce user visibility (for example, by launching the browser in a less noticeable state). Telemetry required is process creation events with the image name and full command line arguments for the spawned browser process.
references:
  - https://twitter.com/mrd0x/status/1478116126005641220
  - https://lolbas-project.github.io/lolbas/Binaries/Msedge/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_browsers_inline_file_download.yml
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2022-01-11
modified: 2025-10-27
tags:
  - attack.command-and-control
  - attack.t1105
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    Image|endswith:
      - \brave.exe
      - \chrome.exe
      - \msedge.exe
      - \opera.exe
      - \vivaldi.exe
  selection_http:
    CommandLine|contains: http
  selection_extensions:
    - CommandLine|endswith:
        - .7z
        - .dat
        - .dll
        - .exe
        - .hta
        - .ps1
        - .psm1
        - .txt
        - .vbe
        - .vbs
        - .zip
    - CommandLine|contains:
        - .7z"
        - .dat"
        - .dll"
        - .hta"
        - .ps1"
        - .psm1"
        - .txt"
        - .vbe"
        - .vbs"
        - .zip"
  condition: all of selection_*
falsepositives:
  - Unknown
level: medium
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_browsers_inline_file_download/info.yml
license: DRL-1.1
related:
  - id: 94771a71-ba41-4b6e-a757-b531372eaab6
    type: derived

What it detects

This rule identifies Windows executions of common browser processes where the command line includes an inline URL containing an HTTP scheme and ends with one of several potentially risky file extensions. Attackers can abuse browser invocation with a URL to trigger downloads of arbitrary payloads or reduce user visibility (for example, by launching the browser in a less noticeable state). Telemetry required is process creation events with the image name and full command line arguments for the spawned browser process.

Known false positives

  • Unknown

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