Which port is commonly used for unencrypted FTP transfers?

• A. 80
• B. 443
• C. 21
• D. 22

Answer: (C)

FTP uses a control channel to send commands and a separate data channel for file transfers. The standard control connection for FTP is on port 21, which is the port typically used for unencrypted FTP transfers. Because this traffic is not encrypted, credentials and commands travel in plaintext over that channel (and the data channel, if data is transferred, is also not encrypted unless encryption is added). The other ports you see—80 for HTTP, 443 for HTTPS, and 22 for SSH—serve different protocols and aren’t used for unencrypted FTP. So, port 21 is the one that’s commonly used to initiate and manage unencrypted FTP sessions.