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 automatic logouts and security banners

Best security practice dictates that people log out of their computers before they walk away from their desks. This is especially important when an administrator uses his or her cubicle computer to remotely log in to a sensitive server. By default, SSH allows a person to remain logged in forever without complaining. However, you can set it up to automatically log out idle users. We’ll look at two quick methods for doing that.

Configuring automatic logout for both local and remote users

This first method will automatically log out idle users who are logged in either at the local console or remotely via SSH. Go into the /etc/profile.d/ directory and create the autologout.sh file with the following contents:

TMOUT=100
readonly TMOUT
export TMOUT

This sets a timeout value of 100 seconds. (TMOUT is a Linux environmental variable that sets timeout values.)

Set the executable permission for everybody:

sudo...