Book Image

Practical Linux Security Cookbook

By : Michael A Lindner, Tajinder Kalsi
Book Image

Practical Linux Security Cookbook

By: Michael A Lindner, Tajinder Kalsi

Overview of this book

With the growing popularity of Linux, more and more administrators have started moving to the system to create networks or servers for any task. This also makes Linux the first choice for any attacker now. Due to the lack of information about security-related attacks, administrators now face issues in dealing with these attackers as quickly as possible. Learning about the different types of Linux security will help create a more secure Linux system. Whether you are new to Linux administration or experienced, this book will provide you with the skills to make systems more secure. With lots of step-by-step recipes, the book starts by introducing you to various threats to Linux systems. You then get to walk through customizing the Linux kernel and securing local files. Next you will move on to manage user authentication locally and remotely and also mitigate network attacks. Finally, you will learn to patch bash vulnerability and monitor system logs for security. With several screenshots in each example, the book will supply a great learning experience and help you create more secure Linux systems.
Table of Contents (17 chapters)
Practical Linux Security Cookbook
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Understanding the bash vulnerability through Shellshock


Shellshock, or Bashdoor, is a vulnerability that's used in most versions of the Linux and Unix operating systems. It was discovered on September 12, 2014, and it affects all the distributions of Linux using a bash shell. The Shellshock vulnerability makes it possible to execute commands remotely using environment variables.

Getting Ready

To understand Shellshock, we need a Linux system that uses a version of bash prior to 4.3, which is vulnerable to this bug.

How to do it…

In this section, we will take a look at how to set up our system to understand the internal details of the Shellshock vulnerability:

  1. The first step is to check the version of bash on the Linux system so that we can figure out whether our system is vulnerable to Shellshock. To check the version of bash, we run this command:

    Bash versions from 4.3 and onwards have been reported to be vulnerable to Shellshock. For our example, we are using the Ubuntu 12.04 LTS desktop version...