SSH (Secure Shell) authentication modes are methods used to verify the identity of users and ensure secure access to remote systems. Common SSH authentication modes include password-based authentication, which relies on a secret passphrase, and public key authentication, which uses cryptographic keys for a more secure and convenient login process. Additionally, multi-factor authentication (MFA) can be employed to enhance security by requiring users to provide multiple forms of authentication, such as a password and a one-time code.