Book Image

Practical Linux Security Cookbook - Second Edition

By : Tajinder Kalsi
Book Image

Practical Linux Security Cookbook - Second Edition

By: Tajinder Kalsi

Overview of this book

Over the last few years, system security has gained a lot of momentum and software professionals are focusing heavily on it. Linux is often treated as a highly secure operating system. However, the reality is that Linux has its share of security ?aws, and these security ?aws allow attackers to get into your system and modify or even destroy your important data. But there’s no need to panic, since there are various mechanisms by which these ?aws can be removed, and this book will help you learn about different types of Linux security to create a more secure Linux system. With a step-by-step recipe approach, the book starts by introducing you to various threats to Linux systems. Then, this book will walk you through customizing the Linux kernel and securing local files. Next, you will move on to managing user authentication both locally and remotely and mitigating network attacks. Later, you will learn about application security and kernel vulnerabilities. You will also learn about patching Bash vulnerability, packet filtering, handling incidents, and monitoring system logs. Finally, you will learn about auditing using system services and performing vulnerability scanning on Linux. By the end of this book, you will be able to secure your Linux systems and create a robust environment.
Table of Contents (20 chapters)
Title Page
Copyright and Credits
Contributors
Packt Upsell
Preface
Index

Securing Mail Transfer – SMTP


SMTP or Simple Mail Transfer Protocol is used by email servers. Every email is sent and received by the SMTP server over the SMTP protocol. An MTA, or Mail Transfer Agent, like Postfix can be configured as an email server.

Postfix can be used on a Linux system to route and deliver emails.

Getting ready

To install and configure Postfix, we will be using an Ubuntu server. We will also need a Fully Qualified Domain Name (FQDN) on our server.

How to do it...

In this section, we will see how to install and configure Postfix on an Ubuntu sever and use as per our requirements:

  1. As Postfix is included in Ubuntu's default repositories, installing it becomes easy. To begin the installation, we will run the following command, along with the DEBIAN_PRIORITY=low environmental variable to answer some additional prompts during the installation:
  1. Once the installation starts, the first window will ask for the type of mail configuration. We will select Internet Site for our needs, as...