Here are the steps to secure an SSH connection:
1. Choosing a strong authentication method: Public key authentication is highly recommended for SSH connections. It involves generating a public and private key pair, where the private key is kept secure and the public key is shared with the server. When a client tries to connect to the server, it sends the public key to the server, which then verifies that the key matches the client’s private key.
1. Disabling root login: It’s highly recommended that root login is disabled over SSH, as it’s a common target for attackers. Instead, create a user account with administrative privileges and allow that user to escalate their privileges when necessary.
1. Using a strong password: If you use password authentication, make sure you choose a strong and complex password, composed of uppercase and lowercase letters, numbers and special characters.
1. Firewall and IP restrictions: Limiting access to specific IP addresses or subnets using a firewall or access control lists (ACLs) reduces the attack surface for SSH connections.
1. Regularly updating and patching the SSH server software: Regular updates and patches help to fix security vulnerabilities in the software.
Technical description of the process:
The Secure Shell (SSH) is a cryptographic network protocol for secure data communication. SSH is designed to replace Telnet, which is an insecure protocol, with encrypted communication that secures SSH connections. The following are the technical steps to secure an SSH connection:
1. The client initiates the SSH session by connecting to the SSH server. The SSH server listens on port 22 by default.
1. The client requests authentication from the server. This can be done using passwords or public key authentication.
1. If password authentication is used, the client sends its username and password using an encrypted connection. The server then verifies the credentials and if they’re correct, it allows the user to log in.
1. When using public key authentication, the client sends its public key to the server, which then verifies if the key matches the client’s private key for that user.
1. After authentication, a secure shell session is opened between the client and server. This secure shell session encrypts all data that passes between the client and server.
1. Any commands that the user types in the shell are encrypted and sent to the server. The server then decrypts the data, executes the commands, and sends back the output.
1. Once the session is complete, the client sends a request to close the SSH connection, which then terminates the secure shell session between the client and server.
In summary, securing an SSH connection involves using strong authentication methods, disabling root login, limiting access through firewall and IP restrictions, and regularly updating and patching the SSH server software.
