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Port 21: FTP (File Transfer Protocol)

FTP (File Transfer Protocol) uses TCP port 21 for command and control channels to transfer files between clients and servers.

Protocol
TCP
Category
File Transfer
Common Services
vsftpd, ProFTPD, Pure-FTPd, IIS FTP

What is Port 21 and How Does It Work?

FTP (File Transfer Protocol) uses TCP port 21 for command and control channels to transfer files between clients and servers.

Security Vulnerabilities & Attack Vectors on Port 21

Standard FTP transmits credentials in plaintext, making it vulnerable to sniffing. Use SFTP (Port 22) or FTPS (Port 990) instead.

Auditing & Scanning Port 21 with Nmap

Run the following command to check if Port 21 is reachable and determine service fingerprints:

nmap -p 21 -sV --script ftp-anon,ftp-bounce

Frequently Asked Questions

How do I check if Port 21 is open?
Use cyber-tool.org diagnostic tools or run 'nc -zv 21' in your terminal to verify open socket connections.
Is it safe to leave Port 21 open to the internet?
Exposing Port 21 (FTP (File Transfer Protocol)) publicly introduces potential exposure. Protect it with IP whitelisting, firewalls, and encryption.