Chapter 1, Linux Security Problems, covers various vulnerabilities and exploits in relation to Linux. It also discusses the kinds of security that can be implemented for these exploits. Topics include preparing security policies and security controls for password protection and server security and performing vulnerability assessments of the Linux system. It also covers the configuration of sudo access.

Chapter 2, Configuring a Secure and Optimized Kernel, focuses on the process of configuring and building the Linux kernel and its testing. Topics covered include requirements for building a kernel, configuring a kernel, kernel installation, customization, and kernel debugging. The chapter also discusses configuring a console using Netconsole.

Chapter 3, Local Filesystem Security, looks at Linux file structures and permissions. It covers topics such as viewing file and directory details, handling files and file permissions using chmod, and the implementation of an access control list. The chapter also gives readers an introduction to the configuration of LDAP.

Chapter 4, Local Authentication in Linux, explores user authentication on a local system while maintaining security. Topics covered in this chapter include user authentication logging, limiting user login capabilities, monitoring user activity, authentication control definition, and also how to use PAM.

Chapter 5, Remote Authentication, talks about authenticating users remotely on a Linux system. The topics included in this chapter are remote server access using SSH, disabling and enabling root login, restricting remote access when using SSH, copying files remotely over SSH, and setting up Kerberos.

Chapter 6, Network Security, provides information about network attacks and security. It covers managing the TCP/IP network, configuring a firewall using Iptables, blocking spoofed addresses, and unwanted incoming traffic. The chapter also gives readers an introduction to configuring and using TCP Wrapper.

Chapter 7, Security Tools, targets various security tools or software that can be used for security on a Linux system. Tools covered in this chapter include sXID, PortSentry, Squid proxy, OpenSSL server, Tripwire, and Shorewall.

Chapter 8, Linux Security Distros, introduces the readers to some of the famous distributions of Linux/Unix that have been developed in relation to security and penetration testing. The distros covered in this chapter include Kali Linux, pfSense, DEFT, NST, and Helix.

Chapter 9, Patching a Bash Vulnerability, explores the most famous vulnerability of Bash shell, which is known as Shellshock. It gives readers an understanding of Shellshock vulnerability and the security issues that can arise with its presence. The chapter also tells the reader how to use the Linux Patch Management system to secure their machine and also gives them an understanding of how patches are applied in a Linux system.

Chapter 10, Security Monitoring and Logging, provides information on monitoring logs in Linux, on a local system as well as a network. Topics discussed in this chapter include monitoring logs using Logcheck, using Nmap for network monitoring, system monitoring using Glances, and using MultiTail to monitor logs. A few other tools are also discussed, which include Whowatch, stat, lsof, strace, and Lynis.

To get the most out of this book, readers should have a basic understanding of the Linux filesystem and administration. They should be aware of the basic commands of Linux, and knowledge about information security would be an added advantage.

This book will include practical examples on Linux security using inbuilt tools of Linux as well as other available open source tools. As per the recipe, readers will have to install these tools if they are not already installed in Linux.

Practical Linux Security Cookbook is intended for all those Linux users who already have knowledge of Linux filesystems and administration. You should be familiar with basic Linux commands. Understanding information security and its risks to a Linux system is also helpful in understanding the recipes more easily.

However, even if you are unfamiliar with information security, you will be able to easily follow and understand the recipes discussed.

Since Practical Linux Security Cookbook follows a practical approach, following the steps is very easy.

In this book, you will find several headings that appear frequently (Getting ready, How to do it, How it works, There's more, and See also).

To give clear instructions on how to complete a recipe, we use these sections as follows:

In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The md5sum command will then print the calculated hash in a single line."

Any command-line input or output is written as follows:

telinit 1

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Navigate to Main Menu | Backtrack | Exploitation Tools | Network Exploitation Tools | Metasploit Framework | Msfconsole."

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