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

Secure remote login – SSH


As the internet grew, the security risks related to using SSH also became visible to users. To overcome these security risks, developers released a new tool called Secure Shell or SSH.

It provides the same functionality as Telnet, but in a secure encrypted tunnel.

Getting ready

For the Linux systems, we can use OpenSSH for SSH connections. It is a free tool for Linux and can be installed using apt. We have discussed the installation and configuration of OpenSSH in previous chapters.

How to do it...

In this section, we will see how using SSH instead of Telnet can secure our data:

  1. Once SSH is installed and configured, we can try to connect to the server using SSH as shown here. Enter the password when prompted:
  1. At the same time, if we try to capture the traffic using Wireshark, we get the following details:

In the previous screenshot, we can see in the last lines that a Key Exchange was initiated between the client and server.

  1. When we go through the packets captured, we can...