SSH

SSH (Secure Shell) is a cryptographic network protocol for operating network services securely over an unsecured network. The best-known application of SSH is for remote login to computer systems by users. It provides a secure channel over an unsecured network by using a client-server architecture.

What is SSH

SSH, or Secure Shell, is a protocol that provides a secure channel over an unsecured network in a client-server architecture. It was designed as a replacement for Telnet and other insecure remote shell protocols such as rlogin, rsh, and rexec. SSH uses encryption to secure the connection between a client and a server, ensuring that data transmitted over the network is protected from eavesdropping and tampering.

The protocol was developed by Tatu Ylönen in 1995 in response to a password-sniffing attack at his university. Since then, SSH has become the standard for secure remote login and other secure network services. It is widely used by network administrators to manage systems and applications remotely, providing a secure method to access and control servers.

SSH operates on port 22 by default and supports various authentication methods, including password-based and key-based authentication. It also supports tunneling, forwarding TCP ports, and X11 connections. The protocol is extensible and has been implemented in various software packages, including OpenSSH, which is the most widely used implementation.

SSH runs on TCP and UDP port 22 and is official IANA port.

Security risk

If port 22 is open and the SSH service is running, it could be a target for brute force attacks or exploitation of vulnerabilities in the SSH software. Unauthorized access could lead to data breaches, system compromise, and other security incidents. It is crucial to use strong authentication methods and regularly update the SSH software to mitigate these risks.

In our UFW tutorial you can follow instructions how you can configure UFW to close port 22. Use StackChanges to monitor if the SSH port is closed and stays closed. StackChanges will send an alert if port 22 is open again.