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 System tools – lsof


At times, we face situations where we are unable to unmount a disk as it says that the files are being used, but we are unable to understand which file it is referring to. In such situations, we can check which files are open by which process is running on the system.

This can be done using the lsof command, which means List Open Files. Since Linux considers everything, including directories, devices, sockets, and so on as files, we can use lsof to easily identify all of the files that are open.

Getting ready

To use the lsof command, it is recommended to be logged in from a root account or else use sudo from a non-root account so that the output of the lsof command is not limited.

How to do it...

In this section, we will explore different options that can be used with the lsof command to understand how it works:

  1. If we just run lsof, it will list all of the open files that belong to any active process on the system. If the output is long, we can use the less command to...