Book Image

Mastering Linux Security and Hardening

By : Donald A. Tevault
Book Image

Mastering Linux Security and Hardening

By: Donald A. Tevault

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.
Table of Contents (15 chapters)
Title Page
Packt Upsell
Contributors
Preface

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'll see SSH protocol 1 gradually being completely removed, as has happened with Red Hat and CentOS 7.4.