139,445 - Pentesting SMB

👉 Overview

👀 What ?

Pentesting SMB (Server Message Block), which is a protocol primarily for file sharing, printer sharing, and access to serial ports and miscellaneous communications between nodes on a network, is a critical aspect of cybersecurity testing. The 139,445 ports are often associated with the SMB protocol, and understanding how to pentest these can provide valuable insights into potential vulnerabilities.

🧐 Why ?

The importance of pentesting SMB lies in its widespread use in corporate networks. SMB, being a network protocol, has been a popular target for attackers. If a malicious actor gains access to an organization's SMB, it could lead to data theft, disruption of services, or even a full-scale breach. Therefore, understanding how to perform a penetration test on SMB is vital for identifying and addressing potential security weaknesses before they can be exploited.

⛏️ How ?

Pentesting SMB involves several steps. Firstly, identify open SMB ports in your network using tools like Nmap. Secondly, enumerate SMB to gather information such as a list of shared resources, user names, and group names using tools like Enum4linux. Thirdly, attempt to exploit known vulnerabilities, such as SMB Relay attacks. Tools such as Metasploit can be used for this purpose. Always remember to follow ethical guidelines during a penetration test.

⏳ When ?

Pentesting SMB became a regular practice with the rise of cyber threats and the realization of SMB's vulnerabilities. It became particularly important after the WannaCry ransomware attack in 2017, which exploited a weakness in the SMB protocol.

⚙️ Technical Explanations

Server Message Block (SMB) is a network protocol primarily used for file sharing, printer sharing, and access to serial ports among nodes in a network. It operates over two ports, 139 and 445. Port 139 is typically used for NetBIOS name resolution, while port 445 is used for SMB over TCP.

Pentesting SMB is a crucial aspect of cybersecurity testing due to SMB's widespread use in corporate networks. The process involves several steps.

The first step is to identify open SMB ports in the network, which can be done using tools like Nmap. Nmap is a free and open-source network scanner designed to discover hosts and services on a computer network, thus creating a "map" of the network.

After identifying open ports, the next step is enumeration. This is where we probe further into the system to gather information such as a list of shared resources, user names, and group names. Tools like Enum4linux, a script for enumerating information from Windows and Samba hosts, can be used for this purpose.

The final step is exploitation, where we attempt to exploit known vulnerabilities in the system. A common attack is the man-in-the-middle attack known as SMB Relay. In an SMB Relay attack, an attacker captures an SMB session, modifies it, and forwards it to another host while impersonating a legitimate user. Tools such as Metasploit, a penetration testing framework that makes hacking simple, can be used for this purpose.

It's important to note that all these steps should be conducted ethically and with the appropriate permissions. The goal is to uncover potential vulnerabilities and address them to enhance the security of the network.

For example, if you want to perform the first step of identifying open SMB ports in a network using Nmap, you might use the following command:

nmap -p 139,445 <target IP address>

Here, -p stands for port and 139,445 are the ports you're scanning. Replace <target IP address> with the IP address of the system you're testing. This command will return whether these ports are open on the target system.

The next step is enumeration. Using Enum4linux for this purpose, you might execute the following command:

enum4linux -a <target IP address>

The -a option is for performing all basic enumeration. Again, replace <target IP address> with the IP address of the system you're testing. This command will retrieve and display information like shared resources, user names, and group names from the target system.

The last step is exploitation. An example of this step would be conducting an SMB Relay attack using Metasploit. This is a more complex procedure, so we'll just outline the basic steps:

1. Launch Metasploit by typing msfconsole in the command line.
2. Use the SMB Relay module by typing use exploit/windows/smb/smb_relay.
3. Set the RHOSTS value, which is the target IP address, using set RHOSTS <target IP address>.
4. Finally, execute the exploit by typing run.

Remember, replace <target IP address> with the IP address of the system you're testing. Also, keep in mind that these steps are for educational purposes only and should be executed ethically and with the appropriate permissions.