Improve Linux server security using command line tools

Use command line tools to improve the security of Linux servers

With the rapid development of the Internet and the popularization of information technology, server security has become a very important topic . As a server administrator, you must take a series of measures to protect the security of your server to prevent hacker attacks and data leaks. In the Linux operating system, command line tools are one of the powerful tools to improve server security. This article will introduce some commonly used command line tools and provide corresponding code examples.

1. SSH (Secure Shell) remote login
   SSH is a secure protocol for remote login through encryption. By using SSH, you can operate remotely over a secure communication channel. Prevent passwords from being intercepted by hackers, and security can be further improved through key authentication.

The following is an example of using SSH to remotely log in to the server:

ssh username@server_ip_address

2. fail2ban intercepts malicious IP
   fail2ban is an IP used to detect multiple failed login attempts , and add it to the blocklist. This will greatly improve the security of the server and avoid brute force password cracking.

The following is an example of installing and configuring fail2ban:

sudo apt-get install fail2ban
sudo cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local
sudo vi /etc/fail2ban/jail.local

In the jail.local file, you can configure fail2ban to monitor specific log files, and Set ban rules and times.

3. ufw configuration firewall
   ufw (Uncomplicated Firewall) is a simple and easy-to-use firewall configuration tool in Linux systems. It filters network traffic and protects servers from unauthorized access.

The following is an example of using ufw to configure firewall rules:

sudo apt-get install ufw
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow ssh
sudo ufw enable

4. lynis System Security Audit
   lynis is an open source system security audit tool used to identify potential security issues and vulnerabilities. It performs a comprehensive scan of the server and provides detailed reports for administrators to fix.

The following is an example of using lynis for system security audit:

sudo apt-get install lynis
sudo lynis audit system

lynis will check all aspects of the system, including system configuration, user permissions, firewall settings, etc., and generate a Security Report.

5. logwatch monitoring log
   Logwatch is a log monitoring tool that can regularly analyze server log files and generate summary reports. By examining a server's log activity, you can understand the server's behavior and security posture.

The following is an example of installing and configuring logwatch:

sudo apt-get install logwatch
sudo vi /etc/cron.daily/00logwatch

In the 00logwatch file, you can configure which log files logwatch extracts information from, and Reports are sent to the specified email address.

By rationally using the above command line tools, the security of the Linux server can be greatly improved. Of course, the tools mentioned here are just a few, and there are many other commands that can be used to harden the server. However, no matter which tools are used, administrators are required to continuously monitor and maintain the security of the server to ensure the security of the server.

Note: The examples shown in this article are only applicable to Debian/Ubuntu series Linux distributions. Other distributions may need to fine-tune the commands to adapt to different environments.

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