# Kali Linux Course #544: Using sendemail for Penetration Testing
## Section 1: Introduction to SendEmail
Email communication is a vital component of modern penetration testing. Being able to send emails that simulate phishing attacks, alerts, or notifications can give security professionals a deeper understanding of vulnerabilities related to email systems. In this section, we'll explore the usage of the 'sendemail' tool in Kali Linux, which provides a simple and effective way to send emails from the command line.
### 1.1 What is SendEmail?
SendEmail is a lightweight, command-line SMTP email client written in Perl. It allows users to send emails with ease, regardless of the underlying operating system. While it has various functionalities, it is particularly useful in penetration testing scenarios for sending spoofed emails or testing email-related vulnerabilities.
### 1.2 Installation and Configuration on Kali Linux
To get started with SendEmail, you first need to ensure it is installed on your Kali Linux system. Follow these steps to successfully install and configure SendEmail.
#### Step 1: Install SendEmail
1. **Open Terminal**
Launch your terminal on Kali Linux.
2. **Update Package Repository**
It's always a good practice to update the package repository before installing new software:
sudo apt update
3. **Install SendEmail**
You can install SendEmail using the package manager with the following command:
sudo apt install sendemail
4. **Verify Installation**
After installation, verify that SendEmail is installed successfully by executing:
sendemail –version
This command should output the version of SendEmail installed.
#### Step 2: Configuration
SendEmail can work with various SMTP servers. In penetration testing, you may want to use a local or external SMTP server that allows relaying emails. Here, we will configure SendEmail to send emails via Gmail’s SMTP server (ensure you have a Gmail account for this):
1. **Enable Less Secure Apps**
If you decide to use Gmail, you need to allow less secure apps to access your account (only for testing purposes). Go to your Google Account settings, search for "Less secure app access," and enable it.
2. **Configuration Example**
Here is a basic configuration example to send emails using Gmail's SMTP server:
sendemail -f [email protected] -t [email protected] -u "Test Email" -m "This is a test email sent from Kali Linux using SendEmail." -s smtp.gmail.com:587 -xu [email protected] -xp your_gmail_password -o tls=yes
– `-f`: From address
– `-t`: To address
– `-u`: Subject of the email
– `-m`: Body of the email
– `-s`: SMTP server and port
– `-xu`: SMTP username
– `-xp`: SMTP password
– `-o tls=yes`: Use TLS for the connection
### 1.3 Step-by-Step Usage and Real-World Use Cases
With SendEmail installed and configured, let's look into its functionalities and how they can be applied in real-world penetration testing scenarios.
#### Use Case 1: Sending a Basic Email
This is a simple scenario where you send a basic email to test SMTP configurations.
"`bash
sendemail -f [email protected] -t [email protected] -u "Hello" -m "Just testing SendEmail." -s smtp.gmail.com:587 -xu [email protected] -xp your_gmail_password -o tls=yes
"`
#### Use Case 2: Sending an Email with Attachments
In penetration testing, you might need to send files as attachments (malware samples, payloads, etc.).
"`bash
sendemail -f [email protected] -t [email protected] -u "Email with Attachment" -m "Check the attached file." -s smtp.gmail.com:587 -xu [email protected] -xp your_gmail_password -o tls=yes -a /path/to/file.zip
"`
#### Use Case 3: Sending Bulk Emails
For social engineering exercises, you may want to send bulk emails to multiple recipients.
"`bash
sendemail -f [email protected] -t [email protected], [email protected] -u "Bulk Email" -m "This email is sent to multiple recipients." -s smtp.gmail.com:587 -xu [email protected] -xp your_gmail_password -o tls=yes
"`
#### Use Case 4: Automating Email Alerts
Imagine you are conducting a penetration test and need to inform your team about critical vulnerabilities found. You can use a script to automate alerts:
"`bash
#!/bin/bash
VULN_FOUND="SQL Injection vulnerability detected!"
sendemail -f [email protected] -t [email protected] -u "Vulnerability Alert" -m "$VULN_FOUND" -s smtp.gmail.com:587 -xu [email protected] -xp your_gmail_password -o tls=yes
"`
### 1.4 Detailed Technical Explanations
#### 1.4.1 Protocols and Security
Understanding the underlying protocols can enhance your usage of SendEmail. SendEmail utilizes SMTP (Simple Mail Transfer Protocol), which is a text-based protocol used for sending emails.
– **TLS/SSL**: Transport Layer Security (TLS) and Secure Sockets Layer (SSL) are cryptographic protocols that ensure secure communication over a computer network. Enable these to prevent eavesdropping when sending sensitive information via email.
– **SMTP Authentication**: This is a method used by email clients to verify that the user is allowed to send emails through the SMTP server. Sending emails without authentication can lead to being flagged as spam.
#### 1.4.2 Email Headers
Email headers contain essential information about the email. Understanding headers can be beneficial in penetration testing for spoofing attacks. Here are some important headers:
– **From**: Specifies the sender's email address.
– **To**: Specifies the recipient's email address.
– **Subject**: The topic of the email.
– **Date**: The date and time when the email was sent.
– **Message-ID**: A unique identifier for the email, useful for tracking.
Example of including custom headers:
"`bash
sendemail -f [email protected] -t [email protected] -u "Custom Header Test" -m "This email has custom headers." -s smtp.gmail.com:587 -xu [email protected] -xp your_gmail_password -o tls=yes -o message-id=
"`
### External Reference Links
– [SendEmail Documentation](https://www.sendemail.sourceforge.net/)
– [Kali Linux Official Tools](https://www.kali.org/tools/)
– [SMTP Basics](https://www.digitalcitizen.life/what-is-smtp-and-how-to-use-it/)
– [Email Header Analysis](https://www.lifewire.com/how-to-read-email-headers-1171400)
### 1.5 Conclusion
In this section, we covered the basics of installing and configuring SendEmail on Kali Linux. We also explored various practical use cases for sending emails in penetration testing and provided detailed technical explanations for better understanding. The skills learned here will enhance your capabilities as a penetration tester and help you understand the security implications associated with email communication.
Stay tuned for the next section, where we will delve deeper into advanced features and explore how to craft and send more sophisticated emails for penetration testing.
—
Made by pablo rotem / פבלו רותם