What is SSH and how does it secure remote access?

Short answer

SSH (Secure Shell) is a cryptographic protocol that provides secure remote login and command execution on servers. It replaces insecure protocols like Telnet and rlogin.

How it works

SSH establishes an encrypted connection between a client and server. It uses public-key cryptography for authentication and symmetric encryption for the session. When you connect, the client verifies the server's host key, negotiates a cipher suite, and then encrypts all traffic.

Key-based authentication is preferred over passwords. You generate a key pair, keep the private key secure, and install the public key on the server. SSH also supports tunneling to forward ports securely.

Example

A developer connects to a cloud server with ssh user@server. The session encrypts every keystroke and response, preventing attackers from stealing commands or output even on untrusted networks.

Why it matters

SSH is the industry standard for remote server administration. Without it, credentials and administrative commands would travel in plaintext, exposing critical infrastructure to attackers.