Table of Contents for

Linux Essentials for Cybersecurity, First Edition

Introduction

Introduced as a hobby project in 1991, Linux has become a dominate player in the IT market today. Although technically Linux refers to a specific software piece (the kernel), many people refer to Linux as a collection of software tools that make up a robust operating system.

Linux is a heavily used technology throughout the IT industry, and it is used as an alternative to more common platforms because of its security, low cost, and scalability. The Linux OS is used to power a larger variety of servers, including email and web servers. Additionally, it is often favored by software developers as the platform they code on.

As with any operating system, cybersecurity should be a major concern for any IT professional who works on a Linux system. Because of the large variety of software running on a Linux system, as well as several different versions of Linux (called distributions), cybersecurity can be a complicated process that involves both system users and system administrators.

Regretfully, cybersecurity is often overlooked in books and classes on Linux. Typically, these forms of learning tend to focus on how to use the Linux system, and cybersecurity is often mentioned as an afterthought or considered an advanced topic for highly experience professionals. This could be because the authors of these books and classes feel that cybersecurity is a difficult topic to learn, but ignoring this topic when discussing Linux is a huge mistake.

Why is cybersecurity such an important topic when learning Linux? One reason is that Linux is a true multiuser operating system. This means that even regular users (end users) need to know how to keep their own data secure from other users.

Another reason why cybersecurity is critical is because most Linux operating systems provide a great number of network-based services that are often exposed to the Internet. The prying eyes of millions of people worldwide need to be considered when securing a personal Linux system or the Linux systems for an entire organization.

Our goal with this book is to provide you with the skills a Linux professional should have. The approach we take is a typical “ground-up” approach, but with the unique methodology of always keeping an eye on security. Throughout this book, you will find references to security issues. Entire sections are devoted to security, and a strong emphasis is placed on creating security policies.

Linux is a very large topic, and it is really impossible to cover it entirely in one book. The same is true regarding Linux security. We have made every effort to provide as much detail as possible, but we also encourage you to explore on your own to learn more about each topic introduced in this book.

Thank you, and enjoy your Linux cybersecurity journey.

Who Should Read This Book?

It might be easier to answer the question “who shouldn’t read this book?” Linux distributions are used by a large variety of individuals, including:

•     Software developers.

•     Database administrators.

•     Website administrators.

•     Security administrators.

•     System administrators.

•     System recovery experts.

•      “Big data” engineers.

•     Hackers.

•     Governmental organizations.

•     Mobile users and developers. (Android is a Linux distribution.)

•     Chip vendors. (Embedded Linux is found on many chip devices.)

•     Digital forensic experts.

•     Educators.

The previous list isn’t even a complete list! Linux is literally everywhere. It is the OS used on Android phones. A large number of web and email servers run on Linux. Many network devices, such as routers and firewalls, have a version of embedded Linux installed on them.

This book is for people who want to better use Linux systems and ensure that the Linux systems that they work on are as secure as possible.

How This Book Is Organized

Chapter 1, “Distributions and Key Components,” dives into essential information related to understanding the various parts of Linux. You learn about the different components of the Linux operating system, as well as what a distribution is. You also learn how to install the Linux operating system.

Chapter 2, “Working on the Command Line,” covers the essential commands needed to work within the Linux environment.

Chapter 3, “Getting Help,” provides you with the means to get additional information on Linux topics. This includes documentation that is natively available on the operating system as well as important web-based resources.

Chapter 4, “Editing Files,” focuses on utilities that you can use to edit text files. Editing text files is a critical Linux task because much of the configuration data is stored in text files.

Chapter 5, “When Things Go Wrong,” reviews how to handle problems that may arise in Linux. This chapter provides details on how to troubleshoot system problems within a Linux environment.

Chapter 6, “Managing Group Accounts,” focuses on group accounts, including how to add, modify, and delete groups. Special attention is placed on system (or special) groups as well as understanding the difference between primary and secondary groups.

Chapter 7, “Managing User Accounts,” covers the details regarding user accounts. You learn how to create and secure these account, as well as how to teach users good security practices in regard to protecting their accounts.

Chapter 8, “Develop an Account Security Policy,” provides you with the means to create a security policy using the knowledge you acquired in Chapters 6 and 7.

Chapter 9, “File Permissions,” focuses on securing files using Linux permissions. This chapter also dives into more advanced topics, such as special permissions, the umask, access control lists (ACLs), and file attributes.

Chapter 10, “Manage Local Storage: Essentials,” covers topics related to the concepts of local storage devices. This includes how to create partitions and filesystems, as well as some additional essential filesystem features.

Chapter 11, “Manage Local Storage: Advanced Features,” covers topics related to advanced features of local storage devices. This includes how to use autofs and create encrypted filesystems. You also learn about logical volume management, an alternative way of managing local storage devices

Chapter 12, “Manage Network Storage,” discusses making storage devices available across the network. Filesystem sharing techniques such as Network File System, Samba, and iSCSI are also included.

Chapter 13, “Develop a Storage Security Policy,” provides you with the means to create a security policy using the knowledge you acquire in Chapters 9–12.

Chapter 14, “Crontab and At,” covers two sets of tools that allow you to automatically execute processes at future times. The crontab system allows users to execute programs at regular intervals, such as once a month or twice a week. The at system provides users with a way to execute a program at one specific time in the future.

Chapter 15, “Scripting,” covers the basics of placing BASH commands into a file in order to create a more complex set of commands. Scripting is also useful for storing instructions that may be needed at a later time.

Chapter 16, “Common Automation Tasks,” covers the sort of tasks that both regular users and system administrators routinely automate. The focus of this chapter is on security, but additional automation tasks are demonstrated, particularly those related to topics that were covered in previous chapters.

Chapter 17, “Develop an Automation Security Policy,” provides you with the means to create a security policy using the knowledge you acquire in Chapters 14–16.

Chapter 18, “Networking Basics,” covers the essentials you should know before configuring and securing your network connections.

Chapter 19, “Network Configuration,” covers the process of configuring your system to connect to the network.

Chapter 20, “Network Service Configuration: Essential Services,” covers the process of configuring several network-based tools, including DNS, DHCP, and email servers.

Chapter 21, “Network Service Configuration: Web Services,” covers the process of configuring several network-based tools, including the Apache Web Server and Squid.

Chapter 22, “Connecting to Remote Systems,” discusses how to connect to remote systems via the network.

Chapter 23, “Develop a Network Security Policy,” provides you with the means to create a security policy using the knowledge you acquire in Chapters 18–22.

Chapter 24, “Process Control,” covers how to start, view, and control processes (programs).

Chapter 25, “System Logging,” covers how to view system logs as well as how to configure the system to create custom log entries.

Chapter 26, “Red Hat–Based Software Management,” covers how to administer software on Red Hat–based systems such as Fedora and CentOS.

Chapter 27, “Debian-Based Software Management,” covers how to administer software on Debian-based systems, such as Ubuntu.

Chapter 28, “System Booting,” covers the process of configuring several network-based tools.

Chapter 29, “Develop a Software Management Security Policy,” provides you with the means to create a security policy using the knowledge you acquire in Chapters 26–28.

Chapter 30, “Footprinting,” covers the techniques that hackers use to discover information about systems. By learning about these techniques, you should be able to form a better security plan.

Chapter 31, “Firewalls,” explores how to configure software that protects your systems from network-based attacks.

Chapter 32, “Intrusion Detection,” provides you with an understanding of tools and techniques to determine if someone has successful compromised the security of your systems.

Chapter 33, “Additional Security Tasks,” covers a variety of additional Linux security features, including the fail2ban service, virtual private networks (VPNs), and file encryption.