Mastering Linux Security and Hardening

By : Donald A. Tevault

3.9 (7)

Buy this Book

Mastering Linux Security and Hardening

3.9 (7)

By: Donald A. Tevault

Buy this Book

Overview of this book

This book has extensive coverage of techniques that will help prevent attackers from breaching your system, by building a much more secure Linux environment. You will learn various security techniques such as SSH hardening, network service detection, setting up firewalls, encrypting file systems, protecting user accounts, authentication processes, and so on. Moving forward, you will also develop hands-on skills with advanced Linux permissions, access control, special modes, and more. Lastly, this book will also cover best practices and troubleshooting techniques to get your work done efficiently. By the end of this book, you will be confident in delivering a system that will be much harder to compromise.

Preface

Who this book is for

What this book covers

To get the most out of this book

Get in touch

Free Chapter

Running Linux in a Virtual Environment

The threat landscape

Keeping up with security news

Introduction to VirtualBox and Cygwin

Using Cygwin to connect to your virtual machines

Summary

Securing User Accounts

The dangers of logging in as the root user

The advantages of using sudo

Setting up sudo privileges for full administrative users

Setting up sudo for users with only certain delegated privileges

Advanced tips and tricks for using sudo

Locking down users' home directories the Red Hat or CentOS way

Locking down users' home directories the Debian/Ubuntu way

Enforcing strong password criteria

Setting and enforcing password and account expiration

Preventing brute-force password attacks

Locking user accounts

Setting up security banners

Summary

Securing Your Server with a Firewall

An overview of iptables

Uncomplicated Firewall for Ubuntu systems

firewalld for Red Hat systems

nftables – a more universal type of firewall system

Summary

Encrypting and SSH Hardening

GNU Privacy Guard

Encrypting partitions with Linux Unified Key Setup – LUKS

Encrypting directories with eCryptfs

Using VeraCrypt for cross-platform sharing of encrypted containers

Ensuring that SSH protocol 1 is disabled

Creating and managing keys for password-less logins

Disabling root user login

Disabling username/password logins

Setting up a chroot environment for SFTP users

Summary

Mastering Discretionary Access Control

Using chown to change ownership of files and directories

Using chmod to set permissions values on files and directories

Using SUID and SGID on regular files

The security implications of the SUID and SGID permissions

Using extended file attributes to protect sensitive files

Summary

Access Control Lists and Shared Directory Management

Creating an access control list for either a user or a group

Creating an inherited access control list for a directory

Removing a specific permission by using an ACL mask

Using the tar --acls option to prevent the loss of ACLs during a backup

Creating a user group and adding members to it

Creating a shared directory

Setting the SGID bit and the sticky bit on the shared directory

Using ACLs to access files in the shared directory

Summary

Implementing Mandatory Access Control with SELinux and AppArmor

How SELinux can benefit a systems administrator

Setting security contexts for files and directories

Troubleshooting with setroubleshoot

Working with SELinux policies

How AppArmor can benefit a systems administrator

Looking at AppArmor profiles

Working with AppArmor command-line utilities

Troubleshooting AppArmor problems

Summary

Scanning, Auditing, and Hardening

Installing and updating ClamAV and maldet

Scanning with ClamAV and maldet

SELinux considerations

Scanning for rootkits with Rootkit Hunter

Controlling the auditd daemon

Creating audit rules

Using ausearch and aureport

Applying OpenSCAP policies with oscap

Using SCAP Workbench

More about OpenSCAP profiles

Applying an OpenSCAP profile during system installation

Summary

Vulnerability Scanning and Intrusion Detection

Looking at Snort and Security Onion

Scanning and hardening with Lynis

Finding vulnerabilities with OpenVAS

Web server scanning with Nikto

Summary

Security Tips and Tricks for the Busy Bee

Auditing system services

Password-protecting the GRUB 2 bootloader

Securely configuring BIOS/UEFI

Using a security checklist for system setup

Summary

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Ensuring that SSH protocol 1 is disabled

By this stage in your Linux career, you should already know how to use Secure Shell, or SSH, to do remote logins and remote file transfers. What you may not know is that a default configuration of SSH is actually quite insecure.

SSH protocol version 1, the original SSH protocol, is severely flawed, and should never be used. It's still in most Linux distributions, but fortunately, it's always disabled by default. But, if you ever open your /etc/ssh/sshd_config file and see this:

Protocol 1

Or this:

Protocol 1, 2

Then you have a problem.

The Ubuntu main page for the sshd_config file says that protocol version 1 is still available for use with legacy devices. But, if you're still running devices that are that old, you need to start seriously thinking about doing some upgrades.

As Linux distributions get updated, you&apos...