Windows curl.exe Suspicious Download to Local File Paths

ATT&CK techniques

C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1105Ingress Tool Transfer
Exfiltration
Impact

What it detects

This rule flags process starts of curl.exe on Windows where the command line suggests the download output is written to common user or system locations such as AppData, Temp, Public, Desktop, PerfLogs, ProgramData, or Windows Temp. It also matches curl command lines that end with file extensions commonly used for downloaded content (e.g., .txt, .vbs, .vbe, images, and temporary script/file formats). Attackers commonly use curl to retrieve remote content and stage it locally, so correlating process creation telemetry with suspicious output paths and extensions helps identify likely download-and-stage activity.

Reporting behind it

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Windows curl.exe Suspicious Download to Local File Paths

Pivot detection · T1105 · 9 related

Changelog

v2

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

windows-curl-exe-download-to-local-file-with-suspicious-paths-and-extensions-e218595b

title: Windows curl.exe Suspicious Download to Local File Paths
id: 0a71b113-2ec9-4048-8d53-1c9bf6bf7132
related:
  - id: bbeaed61-1990-4773-bf57-b81dbad7db2d
    type: derived
  - id: 9a517fca-4ba3-4629-9278-a68694697b81
    type: similar
  - id: e218595b-bbe7-4ee5-8a96-f32a24ad3468
    type: derived
status: test
description: This rule flags process starts of curl.exe on Windows where the command line suggests the download output is written to common user or system locations such as AppData, Temp, Public, Desktop, PerfLogs, ProgramData, or Windows Temp. It also matches curl command lines that end with file extensions commonly used for downloaded content (e.g., .txt, .vbs, .vbe, images, and temporary script/file formats). Attackers commonly use curl to retrieve remote content and stage it locally, so correlating process creation telemetry with suspicious output paths and extensions helps identify likely download-and-stage activity.
references:
  - https://twitter.com/max_mal_/status/1542461200797163522
  - https://web.archive.org/web/20200128160046/https://twitter.com/reegun21/status/1222093798009790464
  - https://github.com/pr0xylife/Qakbot/blob/4f0795d79dabee5bc9dd69f17a626b48852e7869/Qakbot_AA_23.06.2022.txt
  - https://www.volexity.com/blog/2022/07/28/sharptongue-deploys-clever-mail-stealing-browser-extension-sharpext/
  - https://github.com/redcanaryco/atomic-red-team/blob/0f229c0e42bfe7ca736a14023836d65baa941ed2/atomics/T1105/T1105.md#atomic-test-18---curl-download-file
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_curl_susp_download.yml
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2020-07-03
modified: 2023-02-21
tags:
  - attack.command-and-control
  - attack.t1105
logsource:
  category: process_creation
  product: windows
detection:
  selection_curl:
    - Image|endswith: \curl.exe
    - Product: The curl executable
  selection_susp_locations:
    CommandLine|contains:
      - "%AppData%"
      - "%Public%"
      - "%Temp%"
      - "%tmp%"
      - \AppData\
      - \Desktop\
      - \Temp\
      - \Users\Public\
      - C:\PerfLogs\
      - C:\ProgramData\
      - C:\Windows\Temp\
  selection_susp_extensions:
    CommandLine|endswith:
      - .dll
      - .gif
      - .jpeg
      - .jpg
      - .png
      - .temp
      - .tmp
      - .txt
      - .vbe
      - .vbs
  filter_optional_git_windows:
    ParentImage: C:\Program Files\Git\usr\bin\sh.exe
    Image: C:\Program Files\Git\mingw64\bin\curl.exe
    CommandLine|contains|all:
      - "--silent --show-error --output "
      - gfw-httpget-
      - AppData
  condition: selection_curl and 1 of selection_susp_* and not 1 of filter_optional_*
falsepositives:
  - Unknown
level: high
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_curl_susp_download/info.yml
simulation:
  - type: atomic-red-team
    name: Curl Download File
    technique: T1105
    atomic_guid: 2b080b99-0deb-4d51-af0f-833d37c4ca6a
license: DRL-1.1

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