Is port 21 (FTP Control) dangerous?

Port 21 is classified as critical risk and should not be exposed to the public internet. It transmits data without encryption, making it vulnerable to eavesdropping and credential theft.

Should port 21 be open on my firewall?

No, port 21 should not be open to the public internet. Block it at the firewall and use encrypted alternatives such as SSH, SFTP, or HTTPS instead.

What transport protocol does port 21 use?

Port 21 (FTP Control) uses the TCP transport protocol and falls under the File Transfer category.

:21 (TCP)

FTP Control

Critical 风险

TCP — File Transfer

端口概览

端口号 21

服务名称 FTP Control

传输协议 TCP

类别 File Transfer

安全风险 Critical

端口范围知名端口 (0-1023)

什么是端口 21?

FTP control channel. Handles authentication, directory listing commands, and file transfer negotiation. Sends usernames and passwords in plaintext.

TCP File Transfer 常用

安全注意事项

端口21（FTP Control）被归类为严重风险。此端口不应暴露在公网上。该服务在未加密的情况下传输数据，容易受到窃听、凭据窃取和中间人攻击。

建议：在防火墙处封锁此端口。改用加密替代方案（SSH、SFTP、HTTPS）。

FTP Control

Embed This Widget

端口概览

什么是端口 21?

安全注意事项

相关端口 — File Transfer

相关术语