21
FTP Control
Critical RiskTCP — File Transfer
Port Overview
Port Number
21
Service Name
FTP Control
Transport Protocol
TCP
Category
File Transfer
Security Risk
Critical
Port Range
Well-Known (0-1023)
What is Port 21?
FTP control channel. Handles authentication, directory listing commands, and file transfer negotiation. Sends usernames and passwords in plaintext.
TCP
File Transfer
Commonly Used
Security Considerations
Port 21 (FTP Control) is classified as critical risk. This port should not be exposed to the public internet. The service transmits data without encryption, making it vulnerable to eavesdropping, credential theft, and man-in-the-middle attacks.
Recommendation: Block this port at the firewall. Use encrypted alternatives (SSH, SFTP, HTTPS) instead.