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 a packet sniffer to monitor network traffic


One of the most widely used command-line packet sniffer or packet analyzer tools for Linux is Tcpdump. It helps to capture or filter TCP/IP packets being transferred or received on a specific interface over the network.

Getting ready

Tcpdump comes pre-installed in most Linux/Unix-based operating systems. If it is not available, we can install it by using the following command:

How to do it...

Once tcpdump has been installed, we can start using it by simply running the command tcpdump:

  1. When we simply run tcpdump, it will start capturing all the packets sent or received on any interface.
  1. If we want to capture the packets that are only on a specific interface, we can do the same as shown in the following screenshot:
  1. The preceding command will capture all the packets received on the defined interface, until manually stopped. If we wish to capture a specific count of packets, we can do so by using the -c option, as follows:
  1. To display the captured packets...