Securing SSH

Introduction

SSH (Secure Shell) is a protocol for securely accessing remote computers. Securing SSH is crucial to protect against unauthorized access and attacks.

Key Concepts

• Encryption: Ensures that data sent over SSH is secure from eavesdropping.
• Authentication: Verifies the identity of users accessing the server.
• Integrity: Ensures that the data has not been altered during transmission.

Configuration Steps

To secure your SSH server, follow these steps:

1. Change the default SSH port: Edit the SSH configuration file:

   sudo nano /etc/ssh/sshd_config

   Change the line:

   Port 22

   To a different port (e.g., 2222).
2. Disable root login: In the same file, find the line:

   PermitRootLogin yes

   Change it to:

   PermitRootLogin no

3. Use SSH key authentication: Generate a key pair:

   ssh-keygen -t rsa -b 4096

   Copy the public key to the server:

   ssh-copy-id user@server_ip

4. Disable password authentication: In the SSH configuration file, find:

   PasswordAuthentication yes

   Change it to:

   PasswordAuthentication no

5. Restart SSH service: After making changes, restart the service:

   sudo systemctl restart sshd

Best Practices

• Keep your software up to date.
• Limit SSH access to specific IP addresses.
• Use a firewall to restrict access to the SSH port.
• Implement two-factor authentication.
• Regularly review your SSH logs for unauthorized access attempts.

FAQ