This week I already wrote a diary about "code reuse" in the malware landscape[1] but attackers also have plenty of tools to generate new samples on the fly. When you received a malicious Word documents, it has not been prepared by hand, it has been for sure automatically generated. Except if you're a "nice" target for attackers and victim of some kind of "APT". The keyword here is "automation". If defenders try to automate as much as possible, attackers too!

Today, Discord is often used by attackers as a nice C2 server[2] and we can find plenty of Python malware that interact with Discord. Most of them are info stealers. I already found plenty of such scripts but today I spotted something else. A script to generate your own RAT ("Remote Access Tool"). The script has a VT score of 7/56[3] (SHA256:f13433cc26702e7b6116e36629625cc798d0ad4b26aa782a551a38ec3dc8ab23). I had to fine tune a bit the script to make it work in my sandbox but the usage is pretty simple:

The script is very simple, it contains the RAT standard code and the provided token is injected into it:

file.write("""import winreg
import ctypes
import sys
import os
import ssl
import random
import threading
import time
import cv2
import subprocess
import discord
from comtypes import CLSCTX_ALL
from discord.ext import commands
from ctypes import *
import asyncio
import discord
from discord import utils
token = '~~TOKENHERE~~'
global appdata
appdata = os.getenv('APPDATA')
client = discord.Client()
bot = commands.Bot(command_prefix='!')
...
...
""".replace("~~TOKENHERE~~", tokenbot))

You can see that the script asks if the script must be compiled. This is achieved using the pyinstaller[4] module.Once completed, you will have a fully standalone PE file ready to be sent to your victims. I uploaded my sample to VT and it got a score of 10/67, not so bad from an attacker's point of view.

Here is a quick overview of the supported bot commands:

[1] https://isc.sans.edu/forums/diary/Code+Reuse+In+the+Malware+Landscape/28216/
[2] https://crawl3r.github.io/2020-01-25/DaaC2
[3] https://www.virustotal.com/gui/file/f13433cc26702e7b6116e36629625cc798d0ad4b26aa782a551a38ec3dc8ab23/details
[4] https://pypi.org/project/pyinstaller/
[5] https://isc.sans.edu/forums/diary/A+Simple+Batch+File+That+Blocks+People/28212/

Xavier Mertens (@xme)
Xameco
Senior ISC Handler - Freelance Cyber Security Consultant
PGP Key