Want to enhance Linux Server security - follow these steps

    Securing a Linux server is essential to prevent unauthorized access, data breaches, and other security issues. Here are some steps to secure a Linux server:

1. Keep Your System Up-to-Date:

   • Use the following commands to update and upgrade your system:

     sql
     sudo apt update
     sudo apt upgrade
     

   • Install security updates automatically using the following command:

     sudo apt install unattended-upgrades
     

   • Configure unattended upgrades using the following command:

     css
     sudo dpkg-reconfigure --priority=low unattended-upgrades
     

2. Use Strong Passwords:

   • Use the following command to change a user password:

     passwd username
     

   • Use a strong password with a combination of uppercase and lowercase letters, numbers, and symbols. Avoid using dictionary words or common phrases. Use a password manager to generate and store strong passwords.
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3. Disable Unused Services:

   • Use the following command to list all running services:

     css
     systemctl list-units --type=service --state=running
     

   • Identify services that you are not using and disable them using the following command:

     bash
     sudo systemctl disable service_name
     

   • Use the following command to prevent services from starting automatically:

     css
     sudo systemctl mask service_name
     

4. Configure Firewall:

   • Use the following command to install the "ufw" firewall:

     sudo apt install ufw
     

   • Use the following commands to allow incoming SSH connections and enable the firewall:

     bash
     sudo ufw allow OpenSSH
     sudo ufw enable
     

   • Use the following command to check the firewall status:

     lua
     sudo ufw status
     

5. Use SSH Key Authentication:

   • Use the following command to generate an SSH key pair:

     ssh-keygen
     

   • Copy the public key to the server using the following command:

     sql
     ssh-copy-id username@server_ip_address
     

   • Disable password authentication by modifying the "sshd_config" file using the following command:

     bash
     sudo nano /etc/ssh/sshd_config
     

   • Change the following lines to "no":

     perl
     PasswordAuthentication no
     ChallengeResponseAuthentication no
     

   • Reload the SSH service using the following command:

     sudo systemctl reload sshd
     

6. Limit User Access:

   • Use the following command to add a user:

     sudo adduser username
     

   • Use the following command to grant sudo access to a user:

     sudo usermod -aG sudo username
     

   • Use the following command to remove a user:

     sudo deluser username
     

   • Use the following command to remove a user's sudo access:

     sudo deluser username sudo
     

7. Enable Two-Factor Authentication:

   • Use the following command to install the "libpam-google-authenticator" package:

     sudo apt install libpam-google-authenticator
     

   • Use the following command to configure two-factor authentication for a user:

     google-authenticator
     

   • Edit the "sshd_config" file using the following command:

     bash
     sudo nano /etc/ssh/sshd_config
     

   • Add the following line:

     bash
     ChallengeResponseAuthentication yes
     

   • Reload the SSH service using the following command:

     sudo systemctl reload sshd
     

8. Monitor System Logs:

   • Use the following command to view the system log:

     bash
     sudo tail -f /var/log/syslog
     

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