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

Creating an ACL for either a user or a group

The normal Linux file and directory permissions settings are okay, but they’re not very granular. With an ACL, we can allow only a certain person to access a file or directory, or we can allow multiple people to access a file or directory with different permissions for each person. If we have a file or a directory that’s wide open for everyone, we can use an ACL to allow different levels of access for either a group or an individual. Toward the end of the chapter, we’ll put what we’ve learned all together in order to manage a shared directory for a group.

You would use getfacl to view an ACL for a file or directory. (Note that you can’t use it to view all files in a directory at once.) To begin, let’s use getfacl to see if we have any ACLs already set on the acl_demo.txt file:

[donnie@localhost ~]$ touch acl_demo.txt
[donnie@localhost ~]$ getfacl acl_demo.txt
# file: acl_demo.txt
# owner...