Book Image

Practical Linux Security Cookbook

By : Michael A Lindner, Tajinder Kalsi
Book Image

Practical Linux Security Cookbook

By: Michael A Lindner, Tajinder Kalsi

Overview of this book

With the growing popularity of Linux, more and more administrators have started moving to the system to create networks or servers for any task. This also makes Linux the first choice for any attacker now. Due to the lack of information about security-related attacks, administrators now face issues in dealing with these attackers as quickly as possible. Learning about the different types of Linux security will help create a more secure Linux system. Whether you are new to Linux administration or experienced, this book will provide you with the skills to make systems more secure. With lots of step-by-step recipes, the book starts by introducing you to various threats to Linux systems. You then get to walk through customizing the Linux kernel and securing local files. Next you will move on to manage user authentication locally and remotely and also mitigate network attacks. Finally, you will learn to patch bash vulnerability and monitor system logs for security. With several screenshots in each example, the book will supply a great learning experience and help you create more secure Linux systems.

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Practical Linux Security Cookbook
Michael A Lindner | Tajinder Kalsi
Apr, 2016 | 276 pages
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Table of Contents (17 chapters)
Practical Linux Security Cookbook
Practical Linux Security Cookbook
Credits
Credits
About the Author
About the Author
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Linux Security Problems
Linux Security Problems
Introduction
The security policy of Linux
Configuring password protection
Configuring server security
Security controls
Conducting integrity checks of the installation medium using checksum
Using the LUKS disk encryption
Making use of sudoers – configuring sudo access
Scanning hosts with Nmap
Gaining a root on a vulnerable Linux system
2
Configuring a Secure and Optimized Kernel
Configuring a Secure and Optimized Kernel
Introduction
Requirements for building and using a kernel
Creating a USB boot media
Retrieving a kernel source
Configuring and building a kernel
Installing and booting from a kernel
Testing and debugging a kernel
Configuring a console for debugging using Netconsole
Debugging a kernel on boot
3
Local Filesystem Security
Local Filesystem Security
Viewing file and directory details using the ls command
Changing the file permissions using the chmod command
Implementing access control list (ACL)
File handling using the mv command (moving and renaming)
Install and configure a basic LDAP server on Ubuntu
4
Local Authentication in Linux
Local Authentication in Linux
User authentication and logging
Limiting the login capabilities of users
Monitoring user activity using acct
Login authentication using a USB device and PAM
Defining user authorization controls
5
Remote Authentication
Remote Authentication
Remote server/host access using SSH
Disabling or enabling SSH root login
Restricting remote access with key-based login into SSH
Copying files remotely
Setting up a Kerberos server with Ubuntu
6
Network Security
Network Security
Managing the TCP/IP network
Using Iptables to configure a firewall
Blocking spoofed addresses
Blocking incoming traffic
Configuring and using the TCP Wrapper
7
Security Tools
Security Tools
Linux sXID
PortSentry
Using Squid proxy
OpenSSL Server
Tripwire
Shorewall
8
Linux Security Distros
Linux Security Distros
Kali Linux
pfSense
DEFT – Digital Evidence and Forensic Toolkit
NST – Network Security Toolkit
Helix
9
Patching a Bash Vulnerability
Patching a Bash Vulnerability
Understanding the bash vulnerability through Shellshock
Shellshock's security issues
The patch management system
Applying patches on the Linux systems
10
Security Monitoring and Logging
Security Monitoring and Logging
Viewing and managing log files using Logcheck
Monitoring a network using Nmap
Using glances for system monitoring
Monitoring logs using MultiTail
Using system tools – Whowatch
Using system tools – stat
Using system tools – lsof
Using system tools – strace
Using Lynis
Index
Index

Disabling or enabling SSH root login

The Linux systems have a root account by default, which is enabled by default. If unauthorized users get SSH root access to the system, it is not a good idea because this will give an attacker complete access to the system.

We can disable or enable the root login for SSH as per our requirements to prevent the chances of an attacker getting access to the system.

Getting ready

We need two Linux systems to be used as a server and client. On the server system, install the package openssh-server, as shown in the preceding recipe.

How to do it…

First, we will see how to disable SSH root login, and then we will also see how to enable it again:

  1. Firstly, open the main configuration file of SSH, /etc/ssh/sshd_config, in any editor.

    sudo nano /etc/ssh/sshd_config

  2. Now look for the line that reads as follows:

    PermitRootLogin yes

  3. Change the value from yes to no. Then, save and close the file:

    PermitRootLogin no

    • The output obtained will be as follows:

  4. Once done, restart the SSH...

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