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

Using IP tables for configuring a firewall


One of the essential steps while securing a Linux system is setting up a good firewall. Most Linux distributions come pre-installed with different firewall tools. Iptables is one such default firewall of Linux distributions. For older versions of Linux kernel, Ipchains was the default firewall.

Getting ready

Since Iptables ships with the Linux distribution, no extra tools need to be installed to use it. However, it is recommended that to use Iptables, we should not use the root account. Instead, use a normal account that has super user access to run the commands efficiently.

How to do it...

We can define different rules using Iptables. These rules are then followed by the kernel when checking the incoming and outgoing traffic packets:

  1. The first thing we shall do on our system is check which version of iptables is installed by using the following command:
  1. Now, we will check whether any rule already exists on the system for Iptables by using the -L option...