Custom Python RAT Builder, (Fri, Jan 7th)

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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:

!kill Kill the bot (disconnect from Discord)
!dumpkeylogger Dump captured keys to the Discoard channel
!exit Exit the bot (process)
!windowstart Start Window logging
!windowstop Stop Window logging
!screenshot Take a screenshot
!webcampic Take picture with the webcam
!message Display a message on the desktop (via MessageBoxW())
!wallpaper Change the desktop background
!upload Upload a file
!shell Remote command execution
!download Download a file
!cd Change current directory
!help Because attackers need some help too 🙂
!write Write something (like on the keyboard)
!clipboard Get clipboard data
!sysinfo Collect system information
!geolocate Collect GeoIP details about the victim
!admincheck Check if bot is running with admin privileges
!uacbypass Try UAC privileges escalation
!startkeylogger Start the keylogger
!stopkeylogger Stop the keylogger
!blockinput Annoy the user[5]
!unblockinput Release the user
!streamwebcam Start webcam recording
!stopwebcam Stop webcal recording
!getdiscordinfo What about the Discord session?
!streamscreen Record multiple screenshots
!stopscreen Stop screen streaming
!shutdown Stop the victim's computer
!restart Reboot the victim's computer
!logoff Logoff the current user
!bluescreen Generate a BSOD (!)
!currentdir Print current directory
!displaydir List files in the direcotry
!dateandtime Return the victim's computer date & time
!listprocess Return the list of running processes
!prockill Try to kill a process
!recscreen Record a video from screen
!reccam Record a video from webcam
!recaudio Record a wav from the internal mic
!delete Delete a file
!disableantivirus Try to disable the AV
!disablefirewall Try to disable the firewall
!audio Play a record file
!selfdestruct Try to wipe the computer
!windowspass Try to collect system credentials
!displayoff Turn off display
!displayon Turn on display
!hide Try to hide a file ("attrib +h")
!unhide Try to unhide a file
!decode Decode Base64
!ejectcd Open CD tray
!retractcd Close CD tray
!critproc Set process as critical
!website Visit a webpage
!distaskmgr Try to disable the task manager
!enbtaskmgr Try to re-enable the task manager
!getwifipass Exfiltrate Wifi passwords

[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

(c) SANS Internet Storm Center. https://isc.sans.edu Creative Commons Attribution-Noncommercial 3.0 United States License.

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