Port 21 — FTP

TCP · Port 21/TCP is used for the File Transfer Protocol (FTP), a standard network protocol for transferring files between hosts. FTP allows users to upload, download, and manage files on remote servers. This port is critical in security contexts as it provides access to sensitive data.

Port Number: 21
Service Name: FTP
Protocol: TCP
Common Software: vsftpd, ProFTPD, FileZilla Server

Security Notes

FTP transmits data in cleartext. Use SFTP or FTPS instead. Brute-force attacks are common.

FAQ

What is port 21 used for?

Port 21 is used for FTP. Port 21/TCP is used for the File Transfer Protocol (FTP), a standard network protocol for transferring files between hosts. FTP allows users to upload, download, and manage files on remote servers. This port is critical in security contexts as it provides access to sensitive data. Common software: vsftpd, ProFTPD, FileZilla Server.

Is port 21 dangerous to leave open?

FTP transmits data in cleartext. Use SFTP or FTPS instead. Brute-force attacks are common.

How do I check if port 21 is open?

Use nmap: nmap -p 21 <target> or check locally: ss -tlnp | rg 21