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

Blocking spoofed addresses


IP spoofing is a very common technique used by attackers to send malicious packets to a server computer. It is the process of creating IP packets with a forged IP address. This is mainly used for performing attacks like Denial of Service (DoS) attacks.

Getting ready

If we wish to block spoofed IP addresses, we need to have a list of those IP address or the domain names from where these spoofed connections are trying to connect.

How to do it...

We will try to create a basic rule set of iptables, using which we will restrict all the incoming packets, except for those that are necessary for us:

  1. The first step will be to create a rule to allow access to the loopback interface so that the services on the system can communicate properly with each other locally. The command to do so is as follows:
iptables -A INPUT -i lo -j ACCEPT

This is necessary for the system to function properly.

  1. Next, we will create the rule for the outbound connections that have been initiated by our system...