Mastering Linux Security and Hardening

Protect your Linux systems from intruders, malware attacks, and other cyber threats, 2nd Edition

Donald A. Tevault

• Éditeur: Packt Publishing
• Année: 2020
• ISBN:
  9781838983598
• Sujet: Informatica
• Sous-sujet: Sistemi operativi

A comprehensive guide to securing your Linux system against cyberattacks and intruders

Key Features

• Deliver a system that reduces the risk of being hacked
• Explore a variety of advanced Linux security techniques with the help of hands-on labs
• Master the art of securing a Linux environment with this end-to-end practical guide

Book Description

From creating networks and servers to automating the entire working environment, Linux has been extremely popular with system administrators for the last couple of decades. However, security has always been a major concern. With limited resources available in the Linux security domain, this book will be an invaluable guide in helping you get your Linux systems properly secured.Complete with in-depth explanations of essential concepts, practical examples, and self-assessment questions, this book begins by helping you set up a practice lab environment and takes you through the core functionalities of securing Linux. You'll practice various Linux hardening techniques and advance to setting up a locked-down Linux server. As you progress, you will also learn how to create user accounts with appropriate privilege levels, protect sensitive data by setting permissions and encryption, and configure a firewall. The book will help you set up mandatory access control, system auditing, security profiles, and kernel hardening, and finally cover best practices and troubleshooting techniques to secure your Linux environment efficiently.By the end of this Linux security book, you will be able to confidently set up a Linux server that will be much harder for malicious actors to compromise.

What you will learn

• Create locked-down user accounts with strong passwords
• Configure firewalls with iptables, UFW, nftables, and firewalld
• Protect your data with different encryption technologies
• Harden the secure shell service to prevent security break-ins
• Use mandatory access control to protect against system exploits
• Harden kernel parameters and set up a kernel-level auditing system
• Apply OpenSCAP security profiles and set up intrusion detection
• Configure securely the GRUB 2 bootloader and BIOS/UEFI

Who this book is for

This book is for Linux administrators, system administrators, and network engineers interested in securing moderate to complex Linux environments. Security consultants looking to enhance their Linux security skills will also find this book useful. Working experience with the Linux command line and package management is necessary to understand the concepts covered in this book.

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Section 1: Setting up a Secure Linux System

In this section, we will set up a practice lab with both Ubuntu and CentOS virtual machines. Windows users will learn how to remotely access Linux machines from Windows.

The section contains the following chapters:

• Chapter 1, Running Linux in a Virtual Environment
• Chapter 2, Securing User Accounts
• Chapter 3, Securing Your Server with a Firewall - Part 1
• Chapter 4, Securing Your Server with a Firewall - Part 2
• Chapter 5, Encryption Technologies
• Chapter 6, SSH Hardening

Running Linux in a Virtual Environment

So, you may be asking yourself: Why do I need to study Linux security? Isn't Linux already secure? After all, it's not Windows. But the fact is, there are many reasons.

It's true that Linux has certain advantages over Windows when it comes to security. These include the following:

• Unlike Windows, Linux was designed from the ground up as a multiuser operating system. So, user security tends to be a bit better on a Linux system.
• Linux offers a better separation between administrative users and unprivileged users. This makes it a bit harder for intruders, and it also makes it a bit harder for a user to accidentally infect a Linux machine with something nasty.
• Linux is much more resistant to viruses and malware infections than Windows is. Certain Linux distributions come with built-in mechanisms, such as SELinux in Red Hat and CentOS, and AppArmor in Ubuntu, that prevent intruders from taking control of a system.
• Linux is a free and open source software. This allows anyone who has the skill to audit Linux code to hunt for bugs or backdoors.

But even with those advantages, Linux is just like everything else that's been created by mankind. That is, it isn't perfect.

Here are the topics that we'll cover in this chapter:

• Looking at the threat landscape
• Why every Linux administrator needs to learn about Linux security
• A bit about the threat landscape, with some examples of how attackers have, at times, been able to breach Linux systems
• Resources for keeping up with IT security news
• Differences between physical, virtual, and cloud setups
• Setting up Ubuntu Server and CentOS virtual machines with VirtualBox, and installing the Extra Packages for Enterprise Linux (EPEL) repository in the CentOS virtual machine
• Creating virtual machine snapshots
• Installing Cygwin on a Windows host so that Windows users can connect to a virtual machine from their Windows hosts
• Using the Windows 10 Bash shell to access Linux systems
• How to keep your Linux systems updated

Looking at the threat landscape

If you've kept up with IT technology news over the past few years, you'll likely have seen at least a few articles about how attackers have compromised Linux servers. For example, while it's true that Linux isn't really susceptible to virus infections, there have been several cases where attackers have planted other types of malware on Linux servers. These cases have included the following:

• Botnet malware: This causes a server to join a botnet that is controlled by a remote attacker. One of the more famous cases involved joining Linux servers to a botnet that launched denial-of-service (DoS) attacks against other networks.
• Ransomware: This is designed to encrypt user data until the server owner pays a ransom fee. But even after paying the fee, there's no guarantee that the data can be recovered.
• Cryptocoin mining software: This causes the CPUs of the server on which it's planted to work extra hard and consume more energy. Cryptocoins that get mined go to the accounts of the attackers who planted the software.

And, of course, there have been plenty of breaches that don't involve malware, such as where attackers have found a way to steal user credentials, credit card data, or other sensitive information.

Some security breaches come about because of plain carelessness. Here's an example of where a careless Adobe administrator placed the company's private security key on a public security blog: https://arstechnica.com/information-technology/2017/09/in-spectacular-fail-adobe-security-team-posts-private-pgp-key-on-blog/.

Why do security breaches happen?

Regardless of whether you're running Linux, Windows, or whatever else, the reasons for security breaches are usually the same. They could be security bugs in the operating system or security bugs in an application that's running on that operating system. Often, a bug-related security breach could have been prevented had the administrators applied security updates in a timely manner.

Another big issue is poorly configured servers. A standard, out-of-the-box configuration of a Linux server is actually quite insecure and can cause a whole ton of problems. One cause of poorly configured servers is simply the lack of properly trained personnel to securely administer Linux servers. (Of course, that's great news for the readers of this book, because—trust me—there's no lack of well-paying IT security jobs.)

And now, in addition to Linux on servers and desktops, we now have Linux on devices that are part of the Internet of Things (IoT). There have been many security problems with these devices, in large part because people just don't know how to configure them securely.

As we journey through this book, we'll see how to do business the right way, to make our servers as secure as possible.

Keeping up with security news

If you're in the IT business, even if you're not a security administrator, you'll want to keep up with the latest security news. In the age of the internet, that's easy to do.

First, there are quite a few websites that specialize in network security news. Examples include Packet Storm Security and The Hacker News. Regular tech news sites and Linux news websites, such as Ars Technica, Fudzilla, The Register, ZDNet, and LXer, also carry reports about network security breaches. And, if you'd rather watch videos than read, you'll find plenty of good YouTube channels, such as BeginLinux Guru.

Finally, regardless of which Linux distribut...