CREST Practitioner Security Analyst (CPSA) Practice

Port 21 is primarily associated with which protocol?

1. Secure Shell

2. File Transfer Protocol

3. Simple Mail Transfer Protocol

4. User Datagram Protocol

The correct answer is: File Transfer Protocol

Port 21 is primarily associated with the File Transfer Protocol (FTP). This protocol is utilized for transferring files across a network. FTP operates in a client-server model, where the client can upload files to or download files from the server using this designated port. The significance of port 21 lies in its role as the command port for FTP connections. When a user initiates an FTP session, the commands to transfer files are sent through this port. Although data transfer usually occurs over a different port (port 20 for active mode), port 21 remains the key point for establishing control of the session. Understanding this association helps reinforce the knowledge of standard ports and the protocols they correspond to, which is vital for security analysts as they manage and assess network traffic and security measures.