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

Defining user authorization controls


Defining user authorization on a computer mainly deals with deciding the activities that a user may or may not be allowed to do. This could include activities such as executing a program or reading a file.

Since the root account has all privileges, authorization controls mainly deal with allowing or disallowing root access to user accounts.

Getting ready

To see how user authorization works, we need a user account to try the commands on. So, we create few user accounts, user1 and user2, to try the commands.

How to do it...

In this section, we will go through various controls that can be applied on user accounts:

  1. Suppose we have two user accounts, user1 and user2. We log in from user2 and then try to run a command, ps, as user1. In a normal scenario, we get this result:

 

  1. Now, edit the /etc/sudoers file and add this line:
User2 ALL = (user1) /bin/ps
  1. After saving the changes in /etc/sudoers, again try to run the ps command from user2 as user1:
  1. Now, if we want to run...