Suspicious Non-Browser Network Communication With Google API — Sigma Rule

Rule metadata and linked tags

Author: Gavin Knapp. Source status: experimental; severity: medium. Source dates: 2023-05-01 / 2025-02-22.

{
  "product": "windows",
  "category": "network_connection"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 492381dfda004b4130d72eb1c5deb240f1fa2ba6ba2e32a40ce8c2bef4e7531a

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Suspicious Non-Browser Network Communication With Google API
id: 7e9cf7b6-e827-11ed-a05b-0242ac120003
status: experimental
description: |
    Detects a non-browser process interacting with the Google API which could indicate the use of a covert C2 such as Google Sheet C2 (GC2-sheet)
references:
    - https://github.com/looCiprian/GC2-sheet
    - https://youtu.be/n2dFlSaBBKo
    - https://services.google.com/fh/files/blogs/gcat_threathorizons_full_apr2023.pdf
    - https://www.tanium.com/blog/apt41-deploys-google-gc2-for-attacks-cyber-threat-intelligence-roundup/
    - https://www.bleepingcomputer.com/news/security/hackers-abuse-google-command-and-control-red-team-tool-in-attacks/
author: Gavin Knapp
date: 2023-05-01
modified: 2025-02-22
tags:
    - attack.command-and-control
    - attack.t1102
logsource:
    product: windows
    category: network_connection
detection:
    selection:
        DestinationHostname|contains:
            # Note: Please add additional google API related domains that might be abused.
            - 'drive.googleapis.com'
            - 'oauth2.googleapis.com'
            - 'sheets.googleapis.com'
            - 'www.googleapis.com'
    filter_optional_brave:
        Image|endswith: '\brave.exe'
    filter_optional_chrome:
        Image|endswith:
            - ':\Program Files\Google\Chrome\Application\chrome.exe'
            - ':\Program Files (x86)\Google\Chrome\Application\chrome.exe'
    filter_optional_google_drive:
        Image|contains: ':\Program Files\Google\Drive File Stream\'
        Image|endswith: '\GoogleDriveFS.exe'
    filter_optional_firefox:
        Image|endswith:
            - ':\Program Files\Mozilla Firefox\firefox.exe'
            - ':\Program Files (x86)\Mozilla Firefox\firefox.exe'
    filter_optional_ie:
        Image|endswith:
            - ':\Program Files (x86)\Internet Explorer\iexplore.exe'
            - ':\Program Files\Internet Explorer\iexplore.exe'
    filter_optional_maxthon:
        Image|endswith: '\maxthon.exe'
    filter_optional_edge_1:
        - Image|contains: ':\Program Files (x86)\Microsoft\EdgeWebView\Application\'
        - Image|endswith:
              - ':\Program Files (x86)\Microsoft\Edge\Application\msedge.exe'
              - ':\Program Files\Microsoft\Edge\Application\msedge.exe'
              - '\WindowsApps\MicrosoftEdge.exe'
    filter_optional_edge_2:
        Image|contains:
            - ':\Program Files (x86)\Microsoft\EdgeCore\'
            - ':\Program Files\Microsoft\EdgeCore\'
        Image|endswith:
            - '\msedge.exe'
            - '\msedgewebview2.exe'
    filter_optional_opera:
        Image|endswith: '\opera.exe'
    filter_optional_safari:
        Image|endswith: '\safari.exe'
    filter_optional_seamonkey:
        Image|endswith: '\seamonkey.exe'
    filter_optional_vivaldi:
        Image|endswith: '\vivaldi.exe'
    filter_optional_whale:
        Image|endswith: '\whale.exe'
    filter_optional_googleupdate:
        Image|endswith: '\GoogleUpdate.exe'
    filter_optional_outlook_exe:
        Image|endswith: '\outlook.exe'
    filter_main_null:
        Image: null
    filter_main_empty:
        Image: ''
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Legitimate applications communicating with the "googleapis.com" endpoints that are not already in the exclusion list. This is environmental dependent and requires further testing and tuning.
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate applications communicating with the "googleapis.com" endpoints that are not already in the exclusion list. This is environmental dependent and requires further testing and tuning.

Source references

• https://github.com/looCiprian/GC2-sheet
• https://youtu.be/n2dFlSaBBKo
• https://services.google.com/fh/files/blogs/gcat_threathorizons_full_apr2023.pdf
• https://www.tanium.com/blog/apt41-deploys-google-gc2-for-attacks-cyber-threat-intelligence-roundup/
• https://www.bleepingcomputer.com/news/security/hackers-abuse-google-command-and-control-red-team-tool-in-attacks/