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IPFYI
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21

FTP Control

Critical Risk

TCP — 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.

Related Ports — File Transfer

20 FTP Data 69 TFTP 82 XFER Utility 115 SFTP (Simple FTP) 117 UUCP Path 139 NetBIOS Session 152 BFTP 191 Prospero
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