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Secure SSH

Overview

Secure Shell (SSH) is a widely used protocol for secure remote access to servers. Properly securing your SSH service is crucial to protect against unauthorized access and potential attacks.

Importance

  • Authentication Security: Ensures that only authorized users can access the server.
  • Data Encryption: Protects data transmitted over the network from eavesdropping.
  • Access Control: Limits the potential impact of compromised accounts.

Steps to Secure SSH

  1. Use SSH Protocol 2:

    • Ensure that your SSH server is configured to use only SSH Protocol 2 for enhanced security.

      Protocol 2

  2. Change the Default Port:

    • Modify the default SSH port (22) to a non-standard port to reduce the risk of automated attacks.

      Port 2222

  3. Disable Root Login:

    • Prevent direct SSH access to the root account by setting PermitRootLogin to no.

      PermitRootLogin no

  4. Use Public Key Authentication:

    • Configure SSH to use key-based authentication instead of passwords for added security.

      PubkeyAuthentication yes

  5. Limit User Access:

    • Specify which users or groups are allowed to connect via SSH using the AllowUsers or AllowGroups directives.

      AllowUsers user1 user2

  6. Implement Additional Security Measures:

    • Consider using tools like Fail2Ban to block repeated failed login attempts.
    • Configure idle timeouts and disable X11 forwarding to minimize exposure.

  7. Restart the SSH Service:

    • After making changes to the sshd_config file, restart the SSH service to apply the new configurations.

      sudo systemctl restart sshd

Best Practices

  • Regularly Update SSH: Keep your SSH server updated to ensure that security patches are applied.
  • Use Strong Key Algorithms: Prefer strong key algorithms like Ed25519 or RSA with a minimum key length of 2048 bits.
  • Monitor SSH Logs: Regularly monitor SSH logs for suspicious activities or unauthorized access attempts.

By following these steps and best practices, you can significantly enhance the security of your SSH service, protecting your Linux server from unauthorized access and potential attacks.