Windows Process: Squirrel.exe Using Download/Update Flags to Fetch Files

Alert on Squirrel.exe/update.exe runs with --download/--update flags and HTTP in the command line.

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windows-process-squirrel-exe-using-download-update-flags-to-fetch-files-1e75c1cc

title: "Windows Process: Squirrel.exe Using Download/Update Flags to Fetch Files"
id: 1c379257-fbad-41ba-a63c-0374a4ee0534
related:
  - id: 45239e6a-b035-4aaf-b339-8ad379fcb67e
    type: similar
  - id: fa4b21c9-0057-4493-b289-2556416ae4d7
    type: obsolete
  - id: 1e75c1cc-c5d4-42aa-ac3d-91b0b68b3b4c
    type: derived
status: test
description: This rule flags Windows process executions where the image path ends with Squirrel.exe or update.exe and the command line includes Squirrel download or update parameters. Attackers can abuse Squirrel.exe, commonly present with Electron-based applications, to retrieve arbitrary external content through automated download/update workflows. The detection relies on process creation telemetry, specifically the executable name and command-line arguments, including HTTP presence.
references:
  - https://lolbas-project.github.io/lolbas/OtherMSBinaries/Squirrel/
  - http://www.hexacorn.com/blog/2019/03/30/sqirrel-packages-manager-as-a-lolbin-a-k-a-many-electron-apps-are-lolbins-by-default/
  - http://www.hexacorn.com/blog/2018/08/16/squirrel-as-a-lolbin/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_squirrel_download.yml
author: Nasreddine Bencherchali (Nextron Systems), Karneades / Markus Neis, Jonhnathan Ribeiro, oscd.community, Huntrule Team
date: 2022-06-09
modified: 2023-11-09
tags:
  - attack.execution
  - attack.stealth
  - attack.t1218
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    Image|endswith:
      - \squirrel.exe
      - \update.exe
  selection_download_cli:
    CommandLine|contains:
      - " --download "
      - " --update "
      - " --updateRollback="
  selection_download_http_keyword:
    CommandLine|contains: http
  condition: all of selection_*
falsepositives:
  - Expected FP with some Electron based applications such as (1Clipboard, Beaker Browser, Caret, Discord, GitHub Desktop, etc.)
level: medium
license: DRL-1.1

What it detects

This rule flags Windows process executions where the image path ends with Squirrel.exe or update.exe and the command line includes Squirrel download or update parameters. Attackers can abuse Squirrel.exe, commonly present with Electron-based applications, to retrieve arbitrary external content through automated download/update workflows. The detection relies on process creation telemetry, specifically the executable name and command-line arguments, including HTTP presence.

Known false positives

Expected FP with some Electron based applications such as (1Clipboard, Beaker Browser, Caret, Discord, GitHub Desktop, etc.)

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