Which service uses port number 22 by default?

The service that uses port number 22 by default is SSH, which stands for Secure Shell. This protocol is commonly utilized for secure remote login and other secure network services over an unsecured network. SSH's main purpose is to allow secure communication between two systems, typically utilized in server management and file transfers.

By using cryptographic techniques, SSH ensures that all data transmitted is encrypted, preventing eavesdropping, connection hijacking, and various attacks. Choosing this specific port number helps standardize access across different systems and contributes to the overall security of the communication process by ensuring that SSH services can be easily identified and managed consistently.

In contrast, SMTP (Simple Mail Transfer Protocol) utilizes port 25, HTTP (Hypertext Transfer Protocol) typically uses port 80, and DNS (Domain Name System) generally operates on port 53. Therefore, SSH’s default port being 22 distinguishes it from these other protocols, which serve different purposes in network communication.