Linux Tactic

Securing Linux Systems: Best Practices and Tools for Cybersecurity

With the rise of cyberattacks and system hijacking, security has become a crucial aspect of any computer system, including Linux distributions. Linux has been known as a secure operating system for decades.

However, the default insecurity of most Linux distributions has become more apparent as cybercriminals develop new ways to exploit vulnerabilities in the system. In this article, we will explore the importance of security for Linux systems and how to enhance the security of popular Linux distributions like RedHat, CentOS, and Ubuntu.

Default Insecurity of Most Linux Distributions

By default, most Linux distributions are not entirely secure for the average user. This is because the developers of these distribution packages do not enable all the required security features.

Some of the common security issues that arise from the default settings of Linux distributions include weak passwords, unnecessary open ports, and unencrypted communication channels. The result is that Linux systems are prone to cyberattacks, which can lead to data breaches, system hijacking, and even crypto-currency mining.

Importance of Security for Linux Systems

Linux systems are widely used in servers, data centers, and other critical infrastructure applications. A security breach in these systems can have significant impacts on an organization’s operations, reputation, and financial status.

Moreover, Linux systems are also used in personal computers and laptops, which contain sensitive data, such as bank statements, passwords, and personal information. Therefore, protecting Linux systems from cyberattacks is an essential aspect of cybersecurity.

Lab Environment

Before we dive into the specifics of securing popular Linux distributions, it’s important to note that we’ll be using a lab environment. A lab environment will allow us to try out different security measures without causing harm to our actual systems.

We’ll be using VirtualBox, a free and open-source virtualization software, and Cygwin, a collection of Unix utilities for Windows, to create our lab environment.

Focus on RedHat, CentOS, and Ubuntu

RedHat, CentOS, and Ubuntu are popular Linux distributions that are widely used in servers and desktops.

Despite their differences, they share a common foundation they are all based on the Debian architecture. Therefore, the security measures that we will discuss in this article will be applicable to these distributions.

Use of Command Line Interface vs. Graphical User Interface tools

Before we delve into the security measures for RedHat, CentOS, and Ubuntu, we need to establish the difference between Command Line Interface (CLI) and Graphical User Interface (GUI) tools.

The CLI tool is a text-based interface that allows users to interact with the operating system through commands. The GUI tool, on the other hand, is a visual-based interface that enables users to interact with the operating system through icons, menus, and windows.

In general, using CLI tools for security tasks is more efficient as it allows for precise control over system configuration and provides detailed logs for auditing purposes. Securing RedHat, CentOS, and Ubuntu


Update the system regularly

One of the most effective ways of securing a Linux system is to keep the system updated. Regular updates ensure that security patches for vulnerabilities are implemented, and system bugs are fixed.

To update the system, use the following command:

sudo apt-get update && sudo apt-get upgrade


sudo yum update

2. Use strong passwords

Weak passwords are the primary reason for cyberattacks on Linux systems.

To create a strong password, use a combination of uppercase letters, lowercase letters, numbers, and symbols. Avoid using predictable words, such as ‘password,’ ‘12345,’ or ‘qwerty.’ Use the following command to update the password:

sudo passwd $USER


Configure a firewall

Configuring a firewall is critical in enhancing the security of a Linux system. A firewall is a software program that controls incoming and outgoing traffic to and from the system.

Use the following command to install and configure a firewall:

sudo apt-get install ufw

sudo ufw enable


sudo systemctl enable firewalld

sudo systemctl start firewalld

4. Use encryption

Encryption is the process of encoding data to ensure that no unauthorized person can access it.

To encrypt your Linux system, use the following command:

sudo apt-get install ecryptfs-utils

sudo ecryptfs-migrate-home -u $USER


sudo yum install ecryptfs-utils

sudo ecryptfs-migrate-home -u $USER

5. Use a VPN

A VPN (Virtual Private Network) is software that encrypts the internet connection, making it difficult for cybercriminals to intercept network traffic.

Use the following command to install and configure a VPN:

sudo apt-get install openvpn

sudo openvpn –config /path/to/config.ovpn


sudo yum install openvpn

sudo openvpn –config /path/to/config.ovpn


In this article, we have explored the importance of Linux system security and how to enhance the security of popular Linux distributions. We have highlighted the default insecurity of most Linux distributions and discussed the use of CLI vs.

GUI tools for security tasks. We have also provided practical tips on securing the RedHat, CentOS, and Ubuntu distributions, including updating the system regularly, using strong passwords, configuring a firewall, using encryption, and using a VPN.

By implementing these measures, you can enhance the security of your Linux system and reduce the risk of cyberattacks.

Proper Usage of Sudo Command

The sudo command is essential for controlling the level of access that a user has on a Linux system. It allows a user to run a command with root privileges.

However, it’s necessary to use proper sudo usage because if not used correctly, it can result in security vulnerabilities in the system. It’s essential to follow some best practices when using sudo:


Use sudo to perform the command as the root user instead of logging in as the root user. 2.

Only grant sudo access to trusted users who need administrative access. 3.

Always log and monitor sudo command usage to detect suspicious activity. 4.

Use the sudoers file to set granular privileges for users and groups.

Restricting Simple Passwords and Enforcing Periodic Resets

Weak passwords are the primary reason for data breaches on Linux systems. Administrators should enforce password policies that limit the use of simple passwords, such as dictionary words or numbers.

Users should also be required to change their passwords periodically, such as once every six months, to prevent hackers from guessing the password. To enforce password policies, the PAM (Pluggable Authentication Module) framework can be used.

PAM provides a flexible authentication mechanism that allows system administrators to configure policies to fit their specific needs. The administrator can use a combination of PAM modules to enforce password policies, such as pam_cracklib, which checks the strength of the password, and pam_tally2, which tracks failed attempts and can lock the user out temporarily.

Temporarily Locking Suspicious or Under Investigation User Accounts

In situations where a user account is under investigation or is suspected of engaging in malicious activity, the administrator should temporarily lock the account to prevent further damage. The PAM system can again be used to implement such a lock.

The pam_tally2 module can be configured to lock the user out temporarily after a certain number of login attempts have failed.

Basic Firewall Setup to Limit Traffic

The firewall is a critical component of Linux system security. It helps to limit outgoing and incoming traffic on the system.

Linux distributions come with a pre-installed firewall, such as Uncomplicated Firewall (UFW) for Ubuntu, that can be configured using command-line tools such as netfilter, tables, and chains. To create a basic firewall setup, we need to define a set of rules that determine which traffic should be allowed and which traffic should be blocked.

The rules can be based on source IP addresses, destination IP addresses, ports, protocols, and interfaces. For example, to allow incoming SSH traffic from a specific IP address, we can execute the following command:

sudo ufw allow from to any port 22

Symmetric and Asymmetric Encryption Algorithms

Encryption is the process of encoding data to make it unreadable by anyone who does not have the encryption key. Symmetric encryption algorithms use the same key for both encryption and decryption.

Asymmetric encryption algorithms use two different keys, a public key for encryption and a private key for decryption. Encrypting Files, Directories, and Disk Volumes

Encrypting files, directories, and disk volumes is an essential step in protecting the data stored on a Linux system.

Linux supports various encryption methods, such as LUKS (Linux Unified Key Setup), dm-crypt, and ecryptfs. LUKS is a disk encryption specification that provides a standard on-disk format for storing encrypted data.

The dm-crypt module provides the encryption functionality, while the LUKS headers provide the metadata to manage the encrypted disks. Ecryptfs is a stacked cryptographic file system that can encrypt both single files and entire directories.

Basic SSH Hardening

SSH (Secure Shell) is a remote administration protocol that allows users to connect to a Linux system securely. SSH can be hardened by disabling remote root login, limiting incoming connections, and using public key authentication instead of passwords.

Chown/Chmod and Basic Access System

The chown and chmod commands are used to manage file ownership and permissions on Linux systems. These commands are fundamental in controlling access to files and directories.

It’s essential to use them appropriately to ensure that sensitive files are accessible only by authorized users.

Access Control Lists for Intermediate to Advanced Users

Access Control Lists (ACLs) provide a more granular level of access control than traditional file permissions. ACLs allow administrators to give specific users or groups permission to perform specific actions or access specific files and directories.

SELinux (RHEL) and AppArmor (Ubuntu)

SELinux (Security-Enhanced Linux) and AppArmor are Mandatory Access Control (MAC) systems that provide additional security features beyond traditional permissions and ACLs. SELinux is used in RedHat-based distributions, while AppArmor is used in Ubuntu-based distributions. Both systems use policies to define the permissions that users, processes, and services are allowed to have on the system.

Virus and Malware Detection and Prevention

Virus and malware detection and prevention are critical in securing a Linux system. ClamAV is an open-source antivirus engine used to scan for viruses and malware on Linux systems.

Additionally, intrusion detection and prevention systems, such as Snort, can be used to detect and prevent network-based attacks.

Complying with Official Security Standards and Using Corresponding Tools

Compliance with official security standards is essential for organizations that store sensitive data on Linux systems. Linux distributions come with tools, such as OpenSCAP (Open Security Content Automation Protocol), that allow administrators to test compliance with various security standards, such as PCI DSS, HIPAA, and SOX.

Intrusion Detection with Snort

Intrusion detection is the process of monitoring network traffic to detect patterns that indicate a potential attack. Snort is an open-source intrusion detection and prevention system that uses signatures and rules to detect malicious Linux Distributions for Security Vulnerability Work

Security Onion, Kali, Parrot, and Black Arch are Linux distributions specifically designed for security professionals.

These distributions come with pre-installed security tools and support for vulnerability assessment, penetration testing, and forensic analysis. These distributions provide a platform for performing security assessments without compromising the security of the production environment.


Securing a Linux system requires a comprehensive approach that includes best practices for password management, appropriate use of sudo, and restricting user accounts as needed. Additionally, implementing a firewall, encrypting data, using access control tools, and complying with security standards are key steps to protect a Linux system.

Linux distributions designed for security professionals provide a platform for vulnerability assessment and penetration testing without compromising production environments. Linux system administrators can use these tools and practices to enhance the security of their systems and reduce the risk of cyberattacks.

In conclusion, securing Linux systems is of utmost importance in today’s cyber-threat landscape. Default insecurities in most Linux distributions make them vulnerable to attacks, such as system hijacking and crypto-currency mining.

By following best practices, such as proper usage of sudo, restricting weak passwords, implementing firewall rules, encrypting files and disk volumes, and utilizing security tools like Snort and OpenSCAP, administrators can significantly enhance the security of their Linux systems. Furthermore, Linux distributions designed for security professionals, like Security Onion, Kali, Parrot, and Black Arch, offer specialized tools for vulnerability assessment and penetration testing.

By prioritizing Linux system security and implementing these measures, users can safeguard their data, protect against cyberattacks, and maintain the integrity of their systems. Remember, proactive security measures can make all the difference in keeping Linux systems safe from evolving threats.

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