Book Image

Mastering Linux Security and Hardening - Third Edition

By : Donald A. Tevault
3.7 (7)
Book Image

Mastering Linux Security and Hardening - Third Edition

3.7 (7)
By: Donald A. Tevault

Overview of this book

The third edition of Mastering Linux Security and Hardening is an updated, comprehensive introduction to implementing the latest Linux security measures, using the latest versions of Ubuntu and AlmaLinux. In this new edition, you will learn how to set up a practice lab, create user accounts with appropriate privilege levels, protect sensitive data with permissions settings and encryption, and configure a firewall with the newest firewall technologies. You’ll also explore how to use sudo to set up administrative accounts with only the privileges required to do a specific job, and you’ll get a peek at the new sudo features that have been added over the past couple of years. You’ll also see updated information on how to set up a local certificate authority for both Ubuntu and AlmaLinux, as well as how to automate system auditing. Other important skills that you’ll learn include how to automatically harden systems with OpenSCAP, audit systems with auditd, harden the Linux kernel configuration, protect your systems from malware, and perform vulnerability scans of your systems. As a bonus, you’ll see how to use Security Onion to set up an Intrusion Detection System. By the end of this new edition, you will confidently be able to set up a Linux server that will be secure and harder for malicious actors to compromise.
Table of Contents (22 chapters)
1
Section 1: Setting up a Secure Linux System
9
Section 2: Mastering File and Directory Access Control (DAC)
12
Section 3: Advanced System Hardening Techniques
20
Other Books You May Enjoy
21
Index

Configuring access control with whitelists and TCP Wrappers

We’ve already locked things down pretty well just by requiring that clients authenticate via key exchange, rather than by username and password. When we prohibit password authentication, the bad guys can do brute-force password attacks against us until the cows come home, and it won’t do them any good. (Although, in truth, they’ll just give up as soon as they find that password authentication has been disabled.) For an extra measure of security, we can also set up a couple of access control mechanisms that will allow only certain users, groups, or client machines to log in to an SSH server. These two mechanisms are:

  • Whitelists within the sshd_config file
  • TCP Wrappers, via the /etc/hosts.allow and /etc/hosts.deny files

Okay, you’re now saying, But what about firewalls? Isn’t that a third mechanism that we can use? And yeah, you’re right. But, we already covered...